heavyhaul

This one bridges a few topics, but I will start it here, and see if it gets moved.

What I have:
-1993 Dodge 2500 4x4 club cab with a 5 speed, owned for 8 years now. Don't want to get rid of the drivetrain. Truck is a bit rough, but still toughest thing I have owned.
-Recently acquired GMC 3500 extended cab 4x4, 5 spd, 5.7 liter gasser, with a 2400 lb dry weight, 10 1/2' camper, in like new shape. The combo was too good of a deal to pass up, but I ended up with a GMC gas powered truck on the down side. It works, but I would really like to use the Cummins in something.

The GMC/camper rig with enough gear and my family in it ready for a week vacation weighed in at 10,500 lbs. The long drive showed us that a crew cab would be a much better configuration, especially when one thinks that the kid will only be getting bigger, not the other way.

The mechanical engine would be nice to keep, as I don't want to be on top of a mountain chasing codes with a truck that won't start because the planets are not aligned correctly. I am not planning a huge horsepower monster, but I do plan to bump it up to the 300 or so range. I don't want to impact reliability/durability or fuel economy too much. As a matter of fact, the farther a tankfull takes us - the better.

I kinda like the F450 or 550 crewcab conversion that will allow me to carry a bit more gear. Budget is limited, but I do want to do a good job.

Suggestions??