1966 Plymouth belvedere back spacing

Hello all,I have a 1966 Plymouth Belvedere with stock spring location and or no wheel well changes.What back spacing if any to run biggest tire with out rubbing?I going to run the mopar steel H wheels and I can have any back spacing.
Iam looking at 15-8 for rear and 15-7 on front.
Help needed Thanks a bunch Donnie

Been dealing with this and found this to work. 8in rim will need 5 in back spacing. 7in on the rear will need an actual 4.5in bs. Any tire with 10.5 section width should work. Mine is 7in rim with 4.5in bs and 275/60/15 MT radials. I have 5/8 in clearance on body side and the same on the spring side. No rubbing in or out so far but it is close. Id probably stay with 255/60 to be safer than what I did. For the front 7in will work but seem a little wide. I'd go 6in on the front.

My 66 Coronet needed 5.5" backspacing on an 8" wide rim to center the tire in the wheel well. The tires have a 10.2" section width.

18x8" rims and 255/45/18 tires