Because I have seen the 7:56 myself and nobody else is even close, I can tell you the top 10 times for X class, just because there’s no actual leaderboard for X doesn’t mean you can’t have WRs around the track.
I have been doing Goliath everyday since I had the game and I can money on the fact that there’s nobody on this game faster than my mate with 7:56. (This has been screenshot for proof)
I only do A class and under so my best is 12:15 in the 2014 HSV. I have done a 12:10 in the VL Walkinshaw but hit a tree too hard near the end. I also have a Top 100 time (13:56) in C class in the Buick GNX.
9:48 in X-999 Ford GT HE CR Boost but 9:40 with the same car in S2-942 form… But the X class tune gives me more 200K more credits in a 6 lap race 1,216K CR and 621.6K XP? Also a lot more Skill Points with the X-999 - currently maxed out at 999
11:07 in S2-914 Ford Mustang Boss 302 HE XP Boost and 10:52 in S2-941… 956K CR and 803.5K XP for 6 laps