Now in 1970 , the wheel they used for this combo was a 15 x 7 steel wheel. I think this also had to be the 450 wheel ( a 14 inch steel center in a 15 inch steel band , the same band they used on the 15 x 7 ralley wheels ) in order to use the 15 x 7 ralley wheel trim ring. This is because the 15 x 7 ralley wheel trim ring will not fit ( correctly ) a standard 15 x 7 steel wheel ( cop or standard wheel).
The inside measurement on a ralley wheel is 12.25 and a standard steel or cop wheel is 13.25.

I guess I will take the abuse if I am wrong on this , but I am pretty sure I am right.

Frank