Time for new tires and rims for the 68 Dart

Go to summit racing and set the filter to 15" wheel, the width you want, and the desired backspacing and you'll see more wheels than you will know what to do with.

"Measuring from the face of the drum to the edge of the spring is 6.25"

What is the measurement from the face to the quarter?

What width and backspace are you looking for?
I still have to measure to the quarter.
Currently with a 245/60-15 with 4.25 bs it rubs the quarter lip at hard turns. There's about 1" space from inside tire to leaf spring so I'd like to get a 4.75" bs. That would still give me 0.50" to the spring and almost 0.50" off the inner lip. I don't see any 4.75" bs unless I move up to an 8" wide wheel (currently 7").