Tires and wheel question.

I'm going through the same thing with my car at this very moment. I measured the outside section width on my 205/60/15 tire (on a 15 x 5.5 rim)to the offset spring and got about 11 inches. I don't think a 275/60/15 will fit without rubbing on a purely stock a-body 8 3/4, which is what I have in now.

I'm having my wheels widened to 15 x 7.5 with 5" BS just in case a 275 series will go in there. The rear is already centered and I have a good inch from the wheel lip. If you get creative with a custom rim I bet it could work with a 275. I'm pretty confident a 265 will work but you are very limited on those. Dunlop makes a 265/50/15. Hope this helps too.