biggest tire ?

[351w fastback]

i have a 67 mustang with a 8.8 rearend. right now i have 15x7 with 225/70 in back. i want to get the biggest tire possible without sticking out past the fender very much. the rearend is like 2 inches narrower than the stock 8 inch was so does that help me? i was thinking about getting 15x8 in back. is it possible to get 275 back there?
thanks

 

[SandSprite]

Maybe check Nick's wheel/tire database. Find the largest rubber you can fit, then play with backspacing accordingly.
http://www.dodgestang.com/mustang.htm

And what 8.8 did you use?

 

[351w fastback]

the chart says it can fit but i was just worried about like the bulge of the side of the tire and rubbing. the 8.8" is from a 94 explorer. 3.73's with limited slip for $175. me and my dad just shortened the longer side and got the shorter axle from another rearend. no problems so far after about 8,000 miles.

 

[SandSprite]

Cool. Do you know exactly how wide it is drum to drum (or disc to disc)? I think it's quite a bit narrower than a stock 67 rear end (59.25"), so you won't need much backspacing.