Bolt pattern
Ansen and E-T both made uni-lug wheels that went down to 4" bolt pattern. I've had a set of each, and sold both to A-body guys years ago. The largest pattern they fit was 4.75". The only ones I've seen were the slot design, and they're apparently very rare. I've only seen a couple of others over the years.
A-body-specific slots aren't particularly hard to find, but 15" can be tricky. I have two full sets of 14s, my spare, and a pair of 15x8.5s.