71 Duster rear tire size

I have SS springs in the stock location. I also use Weld Prostar rims that are 15"x8" with 4.5 bs with 28"x11.5" QTP's.....With a 8"rim,the side wall bulged some and it rubbed the leafs a little so I put on Mr Gasket 7/16" wheel spacers and they didnt rub any more.
Ive gone 12.00's and have NEVER sheared off the studs. The trick is to use "long shank" lug nuts that go thru the rim and spacer.

Im looking to trade my rims for a set of 15"x10" and I think a 4"bs. If someone is interested,PM me here.