10" wide rear wheels springs moved in.What back space can I run?

I ran 7" bs on mine but I had the wheel well moved into the frame rail. I have a set of Weld Draglights for sale 10" if you're looking

no more than 4" to the outside,

unless you trim or bow the 1/4s

I have stock well wells on mine with a stock length Dana 60. I use a 12" wheel with a 7" backspace. Slicks are 10.5w x 29.5

What width rear end and axles are you using or are you using the stock 1965 8 3/4 width rear end? It does make a difference If your using a stock width 1965 rear end and the leaf springs are move into the sub frame 5 or 5.5 inch on the back side on a ten inch rim or a 6 or 6.5 inch on a twelve inch rim works well If not a stock rear end

This is where a tape measure can be really useful.

With the MoPar spring relocation kit & minitubbed to stock location framerail I have 15x10's w/7.25 bs runnin a 13.4 section width tire.