67 Dart Rear tires

I put a 275/40/17 on my '71 Dart with a 17x9 with 5" backspace. The tire made contact with the quarter lip and the springs, but sat in place. A 1/2" spring relocation and a rolled/trimmed quarter lip should make it possible, as long as your rear axle is actually centered in the car.

The only concern I have is the 9.5" wheel and 5" backspacing. With a 9.5" I'd want at least a 5.3" backspace, but really 5.5 or 5.6" would be better. You can always run small spacer if you get too close to the springs. An 18x9.5" with 5" backspace and a 275/35/18 will sit an extra 1/4" further out than mine were, and that will all have to come out of the quarter lip and then some for clearance.

Ideally, with a 9" rim and a 1/2" spring offset, I'd want 5.25" bs, which should be about 1/4" clearance on the springs and the quarter lip with a 275, with extra clearance to be had on the outside from trimming the quarter lip. With a 9.5" wide rim, that's 5.5" of backspace.