Wheel backspacing on Duster w/ 68 B-body rear

Hemihead2 said
Good info- but as they say I’m already butt-hole deep in it… so I have a 68 B-body rear in the car already AND with S/S springs there is a lot of room above the 245/60/14 tire I have on it already-and there is little to no give to the suspension so I’m pretty sure the top of the tire will never contact the wheel opening.

I think I’m going with 15x7” Rallye wheels on the front with 215/70/15 and 15x8 Rallye wheels on the back with 255/60/15. The tire heights are just about 27” for both and the springs will provide a little rake to it.

Any thoughts are much appreciated!

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of course because I'm an OCD mechanical engineer I put my measurements into a spreadsheet so I could quickly play with different combos to estimate tire clearances. assuming it's a wheel vintiques 15x8 with 4.5" BS, that combo according to my measurements should but the outside edge of the tire nearly flush to the outside of the fender.