it would help to know what year and what type of car it is.

IIRC if its OBD2 good luck doing it legally, nearly impossible. Since no OBD2 car will meet our emissions standards or have the necessary equipment.

OBD1 is easier to do, but even then itll only be STATE legal not Federally.

Rupertaker knows vast more information than me, he would be the one i asked , although, i doubt he will tell you HOW to do it, maybe just point you in the right direction.

There are 2 types of legal cars, STATE which is the easiest to do, and FEDERAL , nearly impossible.

STATE legal cars vary from state to state obviously on requirements, some only require a steering wheel and 4 wheels, some require alot more. Check with your local DMV office