this subject has been discussed before and I believe the answer was no. Now it also depends on the year of the rims as per bolt pattern, backspace and offset.
Like with anything else not "factory fit", anything CAN fit, to a degree. The IROC rims DO have the correct bolt pattern spacing, however the offset may or may not allow them to fit and be usable. I am certain that the same era Trans-AM wheels will fit on a STOCK suspension G-body (REGAL), but you must use the rears on the fronts WITH SPACERS, and the fronts on the rears, or get another pair of T/A front wheels. (The 'front' and 'rear' are cast into the inside of the rim; Some also have the offset cast into the inside in millimeters; You may need to use a VERY good wheel cleaner that has ACID in it to get the 'funk' off the inside.) If the wheels do NOT have anything cast or stamped, they MAY be all the same offset. I believe the "different offset" wheels started on the 1989 models, when GM went to using the Australian 9 bolt cover rear ends. I personally have a set of 84 or 85 Firebird or Camaro 15x7 "diamond mesh" gold colored/ aluminum rims on my 71 Skylark coupe. The 86/87 T-type caps or the Trans-Am caps with the retainers fit on them perfectly!
Back spacing is EASY to measure. Offset is not. Offset and back spacing ARE NOT the same. You can figure out the offset from the back spacing not that it matters. For the 70-72 Skylark/GS, an 8" wide wheel wants 4 1/2" back spacing to center the wheel in the wheel well. Doesn't matter if the wheel is 13", 14", 15", 16", or whatever.
