Widest I can go....without tubbing??
 

Does anybody have any idea how wide of tire I would be able to put on a 84 GS? I don't want to tub, but I would fiberglass flares if need be, the car isn't exactly stock, and the 13' rims aren't doing anything about looking mean. I have a set of 17" rims in mind, but no idea how wide I can go. Any info will help.

Depends on how wide the body is and how much offset the wheel has. I'm shooting for 10" in the rear and 9" up front:) Start going too wide and you have to get spacers.

Its plain jane, but we measured it up and have to put on fiberglass flares (kinda like the widebody body kits) so that they will be 10" in the back 8" in the front with the ability of 12" in the back for at the track. Thanks for the info though