With each car, one may opt for any rim style or size, as long as the PI requirements are met.  The final drive ratio MUST be set to 3:30, with the exception of NASCAR chassis.  I'm sorry if this causes any inconveniences, but gears can be sorted out quickly, so this shouldn't be a problem.  Top speed for each class will be limited by the car's highest gear ratio.

GT Cars:
Lotus Evora Type 124
Hiredgun, Matthnt: 726 PI  Sport Pistons and Compression, Street Centrifugal Supercharger, Race Brakes, Front Tires 275mm 
Roscoe:  733 PI  Race Pistons and Compression, Street Centrifugal Supercharger, Race Brakes, Front Tires 275mm
6th Gear Ratio:  1.01

McLaren MP4-12C
Leadfoot:  745 PI  Stock
Oddball:  751 PI  Race Brakes, Front Tires 310mm, Rear Tires 330mm
6th Gear Ratio:  1.03

Jaguar RSR XKR GT
Moesavy:  752 PI Stock (Restriction Sm)
Maxximilllion:  760 PI  Race Brakes, Front Tire 320mm, Rear Tire 350mm 
6th Gear Ratio:  0.99

Chevrolet Corvette C6.R GT2
The LSA:  754 PI  Stock (Restriction Sm)
CBR900RRR:  763 PI  Race Brakes, Front Tires 320mm, Rear Tires 335mm
6th Gear Ratio:  0.95

Ford GT Mk.7
stalkerstang:  761 PI Stock
6th Gear Ratio:  0.94

Chevrolet Stock Car
Ex US Squid:  773 PI  Race Brakes, Race Weight Reduction
Final Drive Ratio:  3.85

Lamborghini Gallardo GT2
Berpdator:  767 PI  Race Brakes, Race Driveline, Front Tires 320mm, Rear Tires 350mm
6th Gear Ratio:  1.20


SGT Cars:
BMW M3 GT2
Pablo:  810 PI  Fully upgraded, no engine swap
6th Gear Ratio:  1.04

Panoz Esperante GTLM
Hunter:  811 PI Fully upgraded
6th Gear Ratio:  0.90

Jaguar RSR XKR GT
Manuel, PPEVIL:  814 PI Fully upgraded
6th Gear Ratio:  0.91

SRT Viper GTS-R
DirtyDawg, ElKuRtI2Q 832 PI Fully upgraded
6th Gear Ratio:  0.79

Aston Martin DBR9
Rodney:  856 PI Remove 1st restrictor (Restriction Sm)
6th Gear Ratio:  0.91

Koenigsegg CCGT
Ghost:  857 PI  (Restriction Sm)
6th Gear Ratio:  1.05

If this list isn't clear enough, just ask and I'll explain things.