I just traded my CJ5 for an 89 D250 with the cummins. It's bone stock and needs some love as far as suspension goes. Anyway, I've toyed with the idea of using it for the truck camper but all the stick...
These trucks have a Vacuum pump on the lower left front corner of the block to make vacuum for the brakes. If this pump is worn your brakes will be Bad.
I have No Trouble keeping up with traffic with either of my 5.9 Cummins trucks, the 96 is Stock but the 92 has been tweeked a little as the 160 HP ones are a sled the way they are. They did add a intercooler in about 91.5 I think.