Some Dodge Power Wagon and M-37 links for you!
http://www.garbee.net/~cabell/ - great stuff here from a guy who repowered with Cummins diesel, 4.8 gears an overdrive, front disc brakes, etc. Claims 70 MPH and I think 15 MPG.
http://www.uglytruckling.com - offer disc brake kits, lots of instructions, 318 conversions, power steering upgrades, etc.
http://www.440magnum-network.com/pages/Dodge_Truck - links to above as well as venders for new wheels and other items