Biggest tire in Stock rear fenderwells

I'm planning on 275/60x15 in my '69 Dart with SS springs and a spring offset kit. I've already bought my 8" wide rims with 4.5" backspacing. I'm going to narrow the existing B-body (installed by prior owner) to center the wheel/tire package in the available space.
Measurements say it shouldn't be too much of a problem.

I don't know OC,

I just put 255-60-15 BFG TAs and Summit chrome alluminum 8" wide with 4.5' back spacing on my '69 Swinger and even with rolled lips I'm here to tell you it is CLOSE! I can only get my baby finger in between the wheel well lip and the tire on the driver's side and I can't quite get in on the passinger side. I swapped out the original 6 leaf springs with new ones but I got 5 leafs. I installed them and it did raise the car a bit but not enough.

I have since ordered 3400 lb Super Stock springs and plan to put them on. I was told that I can expect a 2' lift from them and plus I'll reap the benifits of improved traction. I just wanted to let you know BEFORE you buy that wheel/tire combo.

Good Luck!!