Mods may have to move: I know this is a third gen forum but figured some of you guys wold be able to answer. Came across an 80 1 ton flat-bed 4X4 single cab dually. It's got an old 305 in it with 4 speed. If I were to put a 454 in it, is there a 6 speed I could change out the 4 speed with? If so, would it require alot of modifications or almost easy like putting the T-56 in our cars?