What I do>>>>
(front width of body) - (front with of car) = x
divide by 2, and fill out the space between body and outside of wheels with some scrap pieces of foam, equally on both sides.
Do the same for the rear end, and tape the foam to your wheels.
The foam makes sure the boby lines-up perfectly with the car.
put the body over your car and press down. With a Sharpy mark the center off the bodyposts. pick up the body and with a body reamer make very small holes in the center of the "Sharpy marks"
( best is not to go trough the body yet.) This way you're OK if you ripp of the overspray film before you drill the bodypost holes.
Happend to someone I know a few times ;-)
"Doing left-turns only, means you're missing half the fun..."