Sounds like a street car build?? If that's the case, you can fit a 275/60/15 (28" tall) by simply moving the the front spring hanger the 1/2"-5/8" to the frame rail and the rear hanger/rearend spring perch to match.
If you want to run a taller tire than that, I wouldn't lose sleep over moving the axle back 1/2"-1". Plenty of folks have with great results. roccodart440 comes to mind - and his car is a racecar. For your street car (I'm assuming here), you'll never notice it. Apparently some would lose sleep over it though.
