Doing my 1st restoration and have some questions.

My '50 has the cab & bed off and the body guy is busy getting the metal into primer. I'm working thru some other stuff and wanted to buy new wheels and tires. The truck is all original except for disc brake upgrade on the front and ring & pinion change in the rear. I believe the truck has the original 6 lug stock wheels.

I want to install a set of 70s GM Rally Wheels, the type that came on the Corvette. I've had a tough time finding these in a 6 lug version but located a guy with a set. The problem is that I know there are fit issues with wheels on the older trucks, especially with backspacing and the disc brake upgrade. Can someone direct me to a website or resource to determine how to correctly measure for wheel size and fit? Any good suggestions on where to find this wheel? How have others dealt with this issue? Thanks.

It never costs more to ask and it never costs more to think big.