You can get the tail out faster and keep it out longer by tweaking the tire pressure settings. Rear tire pressure to max, front tire pressure down to between 25 and 27 because you want a softer front tire for more grip and better steering transitions.
Messing with the gears is not really needed most of the time, just drift in Manual trans mode so you can keep it in the gear you want. Changing the final drive ratio IS needed however, take it up into the 4.2 to 4.5 range and tweak from there until you can make an entire drift run in a single gear, or 1 gear change up or down at most
Anti-roll, springs and damping should NEVER be maxed. You want at least a little bit of body roll or you get understeer. Maxing springs just makes the front end bounce which reduces front grip, you want it stiffer than normal but never maxed out. Min/Maxing damping settings produces a sluggish drifter that’s hard to get to drift in the first place AND spins out as soon as it passes the drift angle limit it’s comfortable with. Damping should be a gradual slope front to rear, top to bottom, nothing maxed, nothing zeroed out.
Maxing rear diff for a RWD drifter is fine for low horsepower setups, but when you’ve got mega horsepower, drop it down to 82% on the acceleration setting and tweak from there, 100% on the deceleration setting to aid in off throttle turn-in.
If you’re running a 4WD drifter, max out all accel and decel settings, and set the torque split to 82% rear and tweak from there.
If you’re running a FWD drifter, I can’t help you, I’m not into self torture 
Caster to 5, it helps turn-in to be sharper and faster, there’s a lot less understeer at 5.
My best drift is just over 520K in the Fortune Island downhill in one of the Ford RTR Mustangs.a
You also forgot downforce settings. Max front, minimum rear. You can even avoid installing the rear wing entirely if you want to.
It’s also worth it to increase braking pressure to around 135% and tweak the front to rear pressure split towards the rear, start around 65% and tweak from there.