3rd Gen wheels, what's what?

My son just bought a '90 RS, V6/Auto, high miles but a good driver. It has the standard 15" aluminum wheels on it with fairly worn out tires. I have a like-new set of BFG g-Force 245-50x16 tires that I'm going to donate to his cause but we're trying to find some suitable wheels that wil fit his budget (small).
I've seen several sets of IROC wheels that are labeled Front and Rear, and I must assume they have different backspacing, yet the 15" rims on his car have the same backspacing front and rear. I'm curious why the IROC wheels have different offsets for front and rear yet the stock RS wheels don't, and which one of the IROC wheels (front or rear) has the same offset as the regular wheels?
Also, are the Trans-Am/GTA style wheels the same thing with different offsets front and rear?

According to the data shown on Skulte Performance Designs (manufactures spacers for 3rd Gens), the 82-92 Camaro 16x8" wheels had 0mm offset/4.35" backspace in the front, and 16mm offset/5.00 backspace in the rear. I believe some of the cars came with 4 identical wheels, and required factory supplied spacers, and others came with wheels with different offsets.

Just a "guess"...... I'm not that knowledgable with the 3rd Gen wheels.

yes GTA wheels were different offset front to rear

the spacing was because of suspension and brake upgrades that caused the wheels to differ as well as the optional tire sizes. if your son is on a budget you can usually find a good zet of 16" iroc or z28 wheels anywhere from $50-200. anymore then $50 a rim and your better off buying a brand new wheel.

a +16 offset isn't anything a small spacer can't fix if you find a set of iroc/z28 wheels. in fact my 91 rs has the typical 91-92z28 wheels and they have a 1/8" spacer that came bolted to the hub. the 245/50/16 tire size is perfect for a 16x8 wheel.