George, 1st gen Camaros did not come with a steel wheel (not a rally) in 15x7 or 15x8 rim. The 15x7 rallys are common on mid 70 Monte Carlos, but I am not sure is the base rims were 15x7. Best bet is to look for station wagon wheels from the 70s. But the offset might not be what you are looking for. 15x8 are Corvette rim sizes and their offsets were a little different. Good luck!
If you are referring to Rally Wheels, the "FW" coded Rally is a 15x7 with 4.25 backspace. They are available at swap meets and on eBay, but be aware that their condition could be mis-represented. I bought a set of two and ended up with one bent one. As far as 15x8s, the "AZ" Rally from 69-82 Corvette has a 4" backspace.
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