Rally Numbers Camaro

I'm just trying to get something straight. I am about to buy some rally wheels for my 1968 camaro and am deciding between original and aftermarket. They look the same so thats not really an issue. neither is price because I can get them for the same price. But what were the original ones made of? Surely they werent solid chrome were they? The aftermarket ones claim to be steel with a mirror like chrome face, and the center caps are supposedly a strong ABS chrome plastic. I'm mainly just wondering about the composition of the originals and if they have any real advantage over the new wheels, other than originality...but honestly, my car isnt numbers matching and it doesnt bother me to have reproduction parts on my car.

Thanks in advance