Or,as popular as it is to ruin good big bolts by putting the cabs on late one ton frames,you could probably find a later big rear end that would fit your frame fairly easily. That might get you a better ratio,open drivelines and easier to find u-joints in the deal. For a transmission,even though it's more expensive,I'd look at the NV4500 5 speed. It's still not a 1-1/2 ton tranny,but it'd hold up to all but the biggest loads you could haul.
Speed
