A Friend of mine is looking at buying one and was wondering how big of tires he could put on it with fender triming but no lift?

depends on what kind of fender trimming,you could fit 38's with enough sawzall work

you can usually fit 33s with no trimming on the 79s, a little rubbing maybe if the springs are really sagged. with a little trimming 35 and 36 are fine and with a whole lot the skys the limit

Thanks For the Help.