im putting this quick question on the heavy equp. topic because the "knowledgeable" ones seem to hang out here. im looking at two c7500 gmc's. both have 3126 cats, one has a 6 speed manual and one has a 5spd with a two spd rear. what trans would be a better set up? or should i just hold up my dress and buy a alison auto so the new guys can run it, i have heard they are well built and tuff as hell these days.