Help with Wheels for '62

[rbruno68]

I am having a hard time buying wheels for my '62. I have a stock '62 with a 6X5.5 bolt pattern. I want to keep the truck stock. I have looked at a lot of pictures of trucks with the Chevy car style rally wheel and really like those. I have been shopping for a set for a couple days now. I have looked at both Summit and Jegs. Jegs sells a Jegs brand wheel and wheels from Wheel Vintage. I am having two issues I can't quite figure out. Backspacing is one. I know what backspacing is but not sure exactly what backspacing to have to fit the truck. I would like to by 15X8 for the back and 15X7 for the fronts. I would like the fronts to be ok for disc brakes incase I upgrade at some point. I have a set of the same size wheels for a Camaro. I measured the back spacing on those just as a reference. The 15x8 had a 4 inch back spacing and the 7 had 3.5. All of the 15X7 with 6 lug patters I have seen have a 4.25 back spacing. The 8s seem to have the same. Those that have these rims, what back space are you using?

The other issue is with the center bore. All of the 6 lug I have been able to find has a 4.25 center bore. I only measured the rear on my stock '62 rear and it has a 3.5 boss on the hub that the rim fits on. Has anyone found 6 lug Rally wheels with a 3.5 center bore?

I am not sure if I am missing something or measuring wrong. I see tons of trucks with the car style rally with 6 lugs, but can't seem to get which ones will fit on my truck given the measurements I am getting.

Any advice would be much appreciated.
Rob