OK, so I just got a set of 15x10 and 15x7 cargar street stars brand new. I dont think there should be any problem with them fittin on my 95 z28. What I am not sure about though is the tire sizes. Whats the widest I could go? I was thinking 275, but then what would be the aspet ratio to kep them at about the same hieght as my stock rims and tires? SO i wouldnt have to reprogram my comuter, and would have the sae gap in my wheel well.

 

Hopefully, your 15x10 wheels have a 7.5" backspace.

You need to find a tire with a 25.65" diameter to match the stockers, and avoid reprogramming (assuming your car came from the factory with the 245/50-16 Z-rated tire option). For the back, the typical tire is going to be a "competition" tire like a drag radial (Nitto, BFG, M/T), in 275/50-15. The diameter of those range from 25.6-26.1", and most are recommended for no wider than a 9.5" wide wheel. Hoosier makes a 275/50-15 road race compound tire that is about 25.3-25.6" and will fit on a 10.5" wide wheel.

The only street radial I know of in a comparable size would be the BFG Radial T/A. Their 275/50-15 is 25.9" diameter, and will fit on a wheel from 7.5-11" wide. They also have a 295/50-15, but that is 26.7" diameter.

For the front, consider a 215/65-15 or a 225/60-15 for the "skinny" look.