Going out on another limb here. Read an article about a TWR designed chassis/body that was used by Jaguar, Mazda and Porsche that won several Le Mans races. So my guess is a Jaguar/Mazda/Porsche Le Mans racer.
Just search for The Strange Orphan Story Of The Most Successful Le Mans Car Ever if you are curious. It’s actually an interesting story in racing history!
Car 4 is probably gonna be the XE-S, reference to the word cat and 0-60 in 4.9s I believe
Car 1 Clue 1: Halloween is such a kooky time of year! I love the festive nature of this holiday >>>> Darth Vader Hot wheels Car
Car 2 Clue 1: It may be crazy to hear this but, what comes around goes around >>>> 2017 DeLorean (YES)
Car 3 Clue 1: You never know until you try! The result might make for generations of cherished rivalries and competition. ??
Car 4 Clue 1: If lives were gears this cat would be hitting 60 in less time than it takes to read this clue aloud >>>> 2017 Jaguar F Type
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing! ??
Car 6 Clue 1: Street legal yes, daily driver, probably not. ??
Car 7 Clue 1: Sometimes winning makes for strange bedfellows. ??
Waiting for the E36 Compact 
I’ve learned that these clues are not to be taken literal, but the the first thing i thought when i read “kooky” is Kouki. So i guess a Kouki Nissan
The fact that it says “What comes around, goes around” rather than “What goes around, comes around” throws me off a bit. Idk, might be overthinking it, could be a typo. For now i’ll say Fisker Karma.
Could be referring to an old iconic rivalry, or maybe something that soon might become iconic. Could be anything
Anything with 9 gears that goes from 0-60 in about 4-6 seconds? i dont know many cars with that many gears. I know lexuses… no, Lexi have many gears 
Big wing? Class? A bosozoku car? Perhaps an old(ish) lexus? 
Lol, just any kit car. I’ll say a Radical.
No idea
Car 1: 1998 Nissan Silvia S14 Kouki
Car 2: Fisker Karma. It would give the Model S some competition
Car 3: 1973 Nissan Skyline GT-R (Kenmeri)
Car 4: I’m going to guess the Jeep Renegade Trailhawk because it would be more different than another Grand Cherokee.
Clue 5: One of those crazy Lucas Oil Sprint Cars.
Clue 6: 2015 Radical RXC Turbo
Clue 7: I don’t know, maybe some psychedelic '60s car that’s not VW
clue 4 - could be the F type SVR although we do have the standard and project 7 versions in game
I’ll take a shot at this…
Car #1: Because he said “kooky” and that sounds like “Kouki” (こうき) I’m thinking late model S14?
Car #2: “What goes around comes around” Well Air-cooled Porsche 930’s are known to come around rather aggressively so I’m thinking RWB Porsche (or Ruf)? Also, Porsche purists like to hate on RWB and Nakai-san for what he does so maybe this a a car Karma/ car culture thing?
Car #3: Obviously a Ute or Convertible… Could be related to adventure… I’m thinking Ford Ranchero because Ute and Roadkill tried to go to Alaska with it twice, and could tie into rivalry as RK/ MCM have a rivalry/ fanbase going, and or RK and Gas Monkey Garage.
Car #4: Cat has 9 lives, car with 9 speed gear box? Hellcat? Its gotta be balistically quick to get to 60 in ~2 seconds… I’m saying Rimac Concept One.
Car #5: Class and #BigWangGang … I’m saying BMW M4 GTS. (It’s probably the new Viper ACR but I wanted to be different)
Car #6: I’m going to say Exocet Miata conversion… (again, probably wrong but i’m being different than everyone else saying Radical RXC)
Car #7: The Eagle Talon (also known as a DSM) won the 1990 and 1991 SCCA Touring Car championship, and it is also sold under Mitsubishi as the Eclipse.
Car #1: I’m probably thinking another S14.
Car #2: I can’t say.
Car #3: I can’t say.
Car #4: TRION NEMESIS RR. If it has 2,000 HP, it has to do 0-60 in less than 2.8 seconds (looking at 2.2). If not, then Jaguar XE-S or Rimac Concept_One (aka the electric Holy Trinity slayer). Or I could make the wildest guess and say Devel Sixteen Prototype.
Car #5: Radical RXC Turbo? If not, then 2016 Dodge Viper ACR.
Car #6: I don’t know. Maybe Morgan 3-Wheeler? Morgan is listed in the game credits. If not the 3-wheeler, then what else could it be? A street legal-converted NASCAR? An unmarked McLaren P1 GTR?
Car #7: Chevrolet Volt?
Car 1 Clue 1: Halloween is such a kooky time of year! I love the festive nature of this holiday
Zenvo ST1
Car 2 Clue 1: It may be crazy to hear this but, what comes around goes around
Tesla Model X or BMW i8
Car 3 Clue 1: You never know until you try! The result might make for generations of cherished rivalries and competition.
Lamborghini 350GT
Car 4 Clue 1: If lives were gears this cat would be hitting 60 in less time than it takes to read this clue aloud
Jaguar F Pace or Jaguar XE S
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing!
Radical SR8 RSX
Car 6 Clue 1: Street legal yes, daily driver, probably not.
Morgan 3-Wheeler
Car 7 Clue 1: Sometimes winning makes for strange bedfellows.
1990 Renaluth Alpine GTA Le Mans or Alpine Vision Concept
I think car 2 clue 1 or car 6 clue 1 could be a NASCAR cuz they have never been in a forza horizon game ever and they can be made street legal.
Car 1 : hot wheels hot rod or kouki
Car 2: Fisker Karma
Car 3: Lamborghini 350GT
Car 4: Acura NSX
Car 5: Dodge Viper ACR
Car 6: Morgan 3-Wheeler or Mercedes 6x6
Car 7: Mercedes 722 SLR
I’m praying that these are the cars because this would be the best car pack ever! The last one was great and blew me away getting the Vulcan AND the Huayra BC so hopefully this one will follow suit of the awesomeness!!!
I think (More hope) clue 7 is the HDT Magnum.
Throughout the 70s and 80s, HDT was Holden’s ‘officially unofficial’ racing team. Under the table funding and through the back door, and the precursor to HSV. In addition to racing, HDT led by racing legend Peter Brock also sold tuned Holden road cars. One of which was the very rare and oft forgotten Magnum, based off the Holden WB Statesman. The Statesman was a full sized luxury car, meant to be competitive with big German cars. It was the Cadillac of Australia.
HDT got a hold of it and cleaned up the looks, put a Holden racing engine in it, classed up the interior, gave it sport suspension, and made a truly high performance luxury saloon. It would lap Bathurst a few seconds off the VK Commodore SS Group 3/A, whilst offering luxury on par with a Mercedes S class.
Clue 1: I feel like the clue is in the kooky and Halloween part, but I’m coming up blank. So, I’ll guess Ford Festiva because of ‘festival’.
Clue 2: something with a wan.kel, perhaps? RX9 concept or older RX7
Clue 3: I’m thinking something old… Like Model T old.
Clue 4: Obvious Jaguar XE lol.
Clue 5: Thinking on it still…
Clue 6: Caparo T1
Clue 7: Collaboration of some sort. Still thinking on it.
Okay, here are my guesses:
Car 1 Clue 1: Halloween is such a kooky time of year! I love the festive nature of this holiday.
Answer: 1933 Packard V12 from the Addams Family
Car 2 Clue 1: It may be crazy to hear this but, what comes around goes around.
Answer: Delorean DMC12
Car 3 Clue 1: You never know until you try! The result might make for generations of cherished rivalries and competition.
Answer: BMW i8
Car 4 Clue 1: If lives were gears this cat would be hitting 60 in less time than it takes to read this clue aloud.
Answer: I initially thought Jaguar F-type SVR, but that only has 8 forward speeds and 1 reverse. But I can’t really connect the 2017 Acura NSX with a cat, but at least that has the full 9-speed gearbox.
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing!
Answer: RWB Porsche
Car 6 Clue 1: Street legal yes, daily driver, probably not.
Answer: 2016 Viper ACR
Car 7 Clue 1: Sometimes winning makes for strange bedfellows.
Answer: McLaren SLR Stirling Moss
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing!
It could be the Ruf CTR series. The 3 of them on their most crazy specs have big wings that help keep the power down.
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing!
2015 Mercedes-Benz #24 Tankpool24 Racing Truck
I remember seeing somewhere that this DLC will also contain a first to the Horizon Series. This would fit the bill.
Clue 7 could be the new fiat 124 spider which is a Mazda mx5
Car 1 Clue 1: Halloween is such a kooky time of year! I love the festive nature of this holiday.
For some reason, two words jump out at me. It would be “kooky” if they added a Ford Festiva/Kia Pride
Car 2 Clue 1: It may be crazy to hear this but, what comes around goes around.
I think this could be a reference to circle or oval tracks, so Hudson Hornet? Unless it’s a reference to cars that notorious for oversteer, in which case it could be a return of the Chevy Corvair or DMC.
Car 3 Clue 1: You never know until you try! The result might make for generations of cherished rivalries and competition.
I’m hoping this is the '65 Mustang GT Coupe. Chevrolet execs initially heard that Ford was developing a sporty car based on the Falcon, and the laughed and asked, “Who’s going to buy that?” When they sold a million in a little over two years, they realized the answer was, “Darn near everybody!”
Car 4 Clue 1: If lives were gears this cat would be hitting 60 in less time than it takes to read this clue aloud.
It took about 5-6 seconds to read this aloud, and the Jaguar XE can make 60 in about that time frame, depending on the engine, so that’s my guess.
Car 5 Clue 1: It takes class to inspire this kind of driving. Well, that and one helluva big wing!
Bentley is known for class, and the Continental GTR-3 has a pretty big wing. I’m going with that for my guess.
Car 6 Clue 1: Street legal yes, daily driver, probably not.
I’m thinking this is a Lotus Exige Sport 350, since that’s a track car that is street legal.
Car 7 Clue 1: Sometimes winning makes for strange bedfellows.
Maybe the MX-5-based Fiat 124? I wouldn’t mind having that in the game!
I believe this is a Hurst
Polaris Slingshot (I mean we already have one three wheeled vehicle, so why not another??)
The rest i have no clues on what they might be