The dusters are like the barracuda's. A 275 will fit with no modifications at all. I have 295's on my Duster with a 1/2" spring offset and some quarter lip trimming.
3/4" offset, wheel lips slightly rolled, front of rear fender rolled under and trimmed to look like stock, (made and used an exact template of wheelwell), dana 60 w/ disc brakes, running 295-65-15 drag radials, w/ cal trac system. ---68 fastback
