275/60 on a Demon?

75dart sport, I'm looking to run the same combination on my 74 Duster.
I want to put 15x8 w/4.5'" backspace rallys, with 275/60/15 tires.
I have the tires on now with 15x7 rallys 4.125 backspace, and needed a 1/4" spacer for the tires to clear the springs. I assume that I'll need a offset hanger kit for the 15x8's, but I have stock inner wells.
Are you wells tubbed? If not how much clearance do you have?
I want the car to sit stock height and don't want to tub the wells.