The Stovebolt Site Forums The Shop Area General Truck Talk wheels for a 66 GMC 8 lug truck

Would someone please tell me if wheels from a 2001 GMC 2500HD will fit a 1966 GMC 3/4 ton truck (both 8 lug of course)? I am looking to put steel wheels (not aluminum)on my old truck. I tried one on the back and it seemed as if I actually had an extra 1/2 inch between the rim edge and the rear leaf spring(when I measured) of back space by using the newer wheel on it. Does anyone know the actual backspace of the newer wheel and the load rating? I came up with 5 inches of back space from the old 6 inch split rim. I wish the center caps would fit on the back (they hit on the axle and therefor don't reach the wheel). Does anyone have any solutions to this? Thanks for your help!