my father has a 94 like that with tbi and six lugs. the lug studs are larger than the regular half ton, so some rims dont fit. keep it stock and they do fine, dads has 277,681 on the clock. yes its the original engine and yes its getting tired. but it has more than payed for its self as a work truck hauling tractors, implements, hay, bricks, horses, you name it. i HIGHLY recomend you get the biggest trans cooler you can for it as, dads has gone though 2 trannys. i think the problem has been too much heat. (trans cooler built into the radiator) other than that and a leaky engine oil cooler line its been basicaly trouble free. if you turn up the torsion bars a little and put a add-a-leaf to the rear you can run 255x85x16 tires (about like a 33x10). theres alot you can do to increace performance i recomend a throttle body spacer and underdrive pullies as well as better exhaust and (if money permits) a performance chip/reprogram. the price is well worth it as im sure dad would want $4500 for his and its a lot rougher condition than that.
hope this helps
balzer