I did this a while ago and dont remember exactly what i did but I know I used my MINOLTA Toyota 88C-V Race Car that i won from A-Spec like the wind. I won this no problem with the stage 3 turbo kit installed. make sure you change the oil! mine has 1040HP! I only had to make one or two pit stops but im pretty sure it was one less stop as compared to the other cars.
for pitting in long races in general, what ive noticed is that all the cars have a pattern they pit in. if you pit a few laps early even of your gas tank is ok for a while and tires are fine for a while, the rest of the pack will pit like 2 or 3 laps after you and you will be back in front.
hope this helps and good luck!