Sounds interesting. I think that tests have to be done to see how equal the different Vettes are. If they are not, it will end up as a "one make"-thing.
I'm thinking 3 different Vettes
1: ZR1 C6 RM
2: Z06 C6 RM
3. C5R C5
Can't think of another Vette than can be fast enough to compete.
But as I said, tests must be done and all cars have to be stock. (oilchange and broken in engines are concidered as stock).
Also that the GTP's rules and regulations apply, and no aids (TCS, ASM, Active Steering, SRF, Driving line).
Gripreduction: real
Damage: Heavy (if making contact could make you enter the pits (heavy damage can only be repaired in the pits), the risk is to high and will therefor prevent crashes)
In-game penaltys: OFF (we need race-stewards to judge the situations)
Just my 2..