Yeah thats why you have different classes - so the guys in the big boats also have a chance
These are the normal classes for a motorkhana (not sure about autocross):
Class AF - Front Wheel Drive- Production vehicles with a wheelbase from 1800 to 2150mm
Class AR - Rear Wheel Drive- Production vehicles with a wheelbase from 1800 to 2150mm
Class BF - Front Wheel Drive- Production vehicles with a wheelbase from 2151 to 2390mm
Class BR - Rear Wheel Drive- Production vehicles with a wheelbase from 2151 to 2390mm
Class CF - Front Wheel Drive- Production vehicles with a wheelbase from 2391 to 2574mm
Class CR - Rear Wheel Drive- Production vehicles with a wheelbase from 2391 to 2574mm
Class DF - Front Wheel Drive- Production vehicles with a wheelbase 2575mm and over
Class DR - Rear Wheel Drive- Production vehicles with a wheelbase 2575mm and over
Class E - Production vehicles with 4 wheel drive
Class F - Front wheel drive specials
Class G - Rear wheel drive specials
(taken from here)