Z-28 Wheels -- Q(?) inside

[MosportGreen66]

I have been sand blasting a set of 1970 Z28 wheels. I bought them from a guy who had them on his 1972 Chevelle Parts car. I bought the wheel with Pontiac center caps so I figured that they were just add on someone put on though the years. But now I have other reasons to think they are Pontiac wheels. The build date on the inside of the wheel is 12-1-78. I thought Pontiac never put these wheels on a Trans Am -- Or did they? I know Chevrolet used these wheels on the 1970-1973 Camaro, 1971-1972 Chevelle and some 1974-197? Camaro as well. Any insight would be helpful.

-Dan