My 383 stroked sbc would have been perfect for your truck. Only produced 320 hp @ 4050 rpm but knocked out 516 lb/ft @ 2800. My current engine is a Dart block 427 sbc and for a heavy truck would not be too good. However a big block 427 would have more than enough torque at low rpm to get the weight of the truck going good AND would also have the high rpm zing factor.