I ran a junkyard 3 speed that came from a 66 Chevelle 6 banger behind a mild 400 sbc, Isky 30/30 cam, headers and 650 dp with no problems in a 62 half ton. I had a 3100 lb pressure plate built for that combination and ran it with the stock hydraulic clutch mechanism. I did go through 3 stock rear ends though.