WILL A 1989 CAB FIT ON A 1982 FRAME?

I believe they were the same through '89, but I would check with a Hollander interchange manual to be sure (most wrecking yards have one of these manuals.)

the cab itself is the same from 80-96, the difference comes in the front fenders and the body line on the box. I put a 81 onto a 90 frame with no problems