I did a ton of research and measuring when I bought wheels for my 1985 G20. I wanted Cragars, but ended up going with Torque-Thrust 2s because they were one of the only wheel designs that came in my ideal calculated sizes for both front and rear.
Here is what the specs are and what it looks like:
Keep in mind:
-I have flairs
-I have drop knuckles in the front that also widened the track about 0.5".
Front: 15x8 with 3.75" backspace / 255/60/15 tire
Rear: 15x10 with 3.77" backspace / 295/50/15 tire