70 Challenger front backspace and width info needed

[hp2]

4.75 is the max you can use with a 15" rim, and that may be a variable measurement since you now have drop spindles. In stock form, anything greater than 4.75" put the rim lip into the upper ball joint. With the drop spindles or a 17"+ rim, you can move to 5 or 5.25 backspace with an 8 inch wide rim. Of course, the more you pull them in, the greater the odds of rubbing the frame rail.