If you're going to run a true square setup i wouldn't run a staggered rim setup. I would run something like 20x9.5 all around with that tire size should be ok. Could be wrong but don't see the point of putting 275s up front and your wheels aren't a square setup. Just my 2 cents.
i know on a true square set up ideally you have all 4 wheels the same but I have what I have. I can keep 255's up front and put the 275's in the rear but I have 4 275's so was just wondering if it would be better to put the up front as well or just leave it staggered.
I have 305's on the rear and my car was lowered prior to storing it. I just took it out for a little spin and it rubs so I have no choice but to go with narrower tires.