largest rear tire without relocating springs or?

How close are those 275's getting to the front edge of the wheel well?

I just went out and measured. There's 3/4" of clearance to the front wheel well on the DS and 5/8" on the PS. Gotta love factory tolerances. That's with the wheel well trim on as well. If it was close enough to rub a little, I wouldn't hesitate to slip a 1/4" thick aluminum spacer behind the front hanger. BTW- my tires are Cooper Cobras. I'm sure each manufacturer's tires are slightly different in size. My wheels have 4.75" of backspacing (custom steelie's from wheel vintiques). They'll make you a custom offset wheel for an extra $25 each.