definately corvette ZR1 racemod, run less rear downforce and full front downforce, get rid of that rear toe in on the full custom suspension. I did a 41.9 sec lap with control pad
best car for the price for this series, it will pay for itself over and over.
Ford GT LM Spec II Test car is probably the best car to drive because it's easy!
Fastest is probably the ZR1 or Z06 Race Modified cars though so thats probably the best choice. Even though i prefer the Ford!!!
this series can easily be done with the 2010 Camaro SS/RM as well, no problem smoking the competition.
It is also a cheap alternative, rather than spending millions on cars that you will unlock doing B-Spec event's
I prefer the Ford GT Spec II over the Corvette Z1 RM just because of the handling It has more grip and is easier to keep on the track. The ZR1 is a fun car though.
Oreca viper and Ford GT II will kill it. Make the gearing a tad longer and don't brake. Guaranteed sub .40 laps. I'm not sure but I feel i average around .35 a lap with these cars.
EDIT: Just realized that you may be talking about both races not just the Indy grind. The above cars will be great. Honestly I beat the second race with a fully modded Saleen S7.