15x28x10.50 Mt sportsman pro's

Sounds to me that you should have bought wheels with more backspace. Since you have room toward the spring, another 1/2" of backspace would give you 1/2" more at the quarter panel. I fit 275-60-15 mt drag radials with just the offset spring package in my duster. Some wheel companies will make special offsets (of course for an extra charge).