i'm in the same boat as you; i'm also looking for a 1ton, but mine will be preferrably crew-cab and diesel. You're lucky to find the truck for 1350.
i would guess the extended fenders need to be checked for cracks as they are fiberglass(i think?), and i think that was/is a somewhat common problem with dually trucks. But even if the fenders are cracked, are you going to pass the truck up just because of that? i wouldn't either. So, what is the remedy? i'm not sure; Tape?
Also, try to find out what the prev. owner used the truck for. If for towing, as many of these trucks were purchased for, then the transmission will need to be checked extra carefully. i'm not real familiar with manuals, but unusual noise(s) would be a start.
i will add more as i learn more.