I've never seen a published gross weight rating for a Tremec 3550/TKO, have you got a source for that number? As for weight it depends on the truck. My 96 regular cab, short box, 2WD 300 weighs in just under 4000#. A stretch cab, long box 4WD 351 is going to chip real hard on that 6000# number. With that cam, I'm assuming he's way more interested in hauling a** than in hauling loads and for that application, the Tremec works just fine