Looking to order 17s

I'm looking more and more into ordering 17s for my 68 valiant that has bbp disc brakes up front, bbp 7.25 rear (eventually 8.75). I'm running a hellwig 1.125 sway bar and 2800 as springs. In a 17x7 about what back spacing would I need to fit a 205/40R17 and a 245/45R17? Sorry if rhis question has been done to death.

There's no answer to that until you determine what rear end you're using, for example; my buddy's blue `69 has an 8.25 rear end, and with my old mustang wheels (17x8 w/ 5.72" backspace) and .75" spacers I cant fit my little fingertip between the leafs and tire. At the same time, he's got miles between the outside of the back tire and the inner fender. The A body 8.75 is wider, but not by much.
BTW he has the same setup as you up front.
By comparison, and since I can't stand using spacers, I'm using a B body 8.75, one and a half inches wider, easier to find, easier to fit wider same size wheels all around, usually bigger drums, and doesn't make the front track wider than the rear since the bbp front end has 1.5" wider track width than the drum setup.
With the 7" width you're suggesting, you could probably use a 4.75 to 5 inch backspace on your existing and future a-body rear without problems, but your wheel wells will scream for more. aloha- pauly

BTW, those ETs are nice!

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