How do you guys fit a tire with 275+ width on the rear?

If you are wanting a 10" wheel, you better make sure you stick with stock length axles or you will never clear them. I assume 10" is what you are calling deep dish. If you use factory length axles you will still more than likely have to remove your quad-shocks. Then to keep from rearend hop, you will probably need a heavy duty lower control arm, like from maximum motorsports. Next you will have to beat the living H3LL out of your inner fenders to shove back the sheet metal far enough. Best to use a torch and hand sledge, you will beat until your arm falls off. Just make sure you dont pinch the springs or bind anything. It is just a trial and error until you get them to clear. Also you need to run a backspacing of somewhere very near 6.5 I believe is best. Needless to say, it is A LOT OF WORK. Otherwise you can go with 9" and a little smaller tire, and probably have no troubles at all. If you want the 10" though, nice thing require a nice amount of work. So be more specific and I can give you a better idea. Also if you have not searched the forum yet, there are MANY things about this.

Alot of people run 275s just fine, no need to beat the crap out of the inner fenders. Just need wheels with the right backspacing. You start havint o beat the fenderwells in when you go to bigger tires or wider wheels.

Are you using the complete rear dif from a sn95?

This is what I did, along with sn95 wheels.
My wheels actually stick to the outboard too far. 255s cleared pretty easy, but my current 275s are too tight of a fit to the outer fender well. I have hammered the lip quite a bit, and have installed a panhard rod (keeps the rear located left/right in respect to the body), but there is still rubbing.

I need to shorten my axles about .100" to .200". There is room for this, as I have a good .250" clearance with the quad shocks.

jason

I have run my 275-50-15 BFG Drag Radials on the back of my 82 Mustang, with cut coils on both 10 holes and the current set of Centerline Convo Pros. I did gently hammer the fender lips, took 30 mins, and I put an airbag in the pass side to help on launches. Otherwise it works fine. Note that I have no back seat, rarely carry a passenger, etc.