5.9 Magnum into a 73Duster

I will let others chime in on the wiring.

For fuel system, I would consider running a complete new system. All of the aftermarket hose vendors (Aeroquip, Russell, and Earls) have a light weight press in hose, that is cheaper and easier to work with the the standard braided hose. Either enlarge the stock pickup, or sump a NEW tank, run a prefilter that is 100 micron before the pump to catch the contaminents, and a 10 micron filter after to catch the really small stuff. You should be able to find the adapters needed to connect this to the stock fuel rail, and then return back to the tank. Return away from the inlet as much as possible to reduce cavitation, the number one killer for electric pumps.

In regards to pumps, spend the extra money up front, or you will later. I prefer and recommend aeromotive, as they are quality built, USA product. They can even be mounted in take if desired... Check out an A1000.