retro fitting Magnum F.I.

The efi magmuns still have a distributor and plug wires. I have 4 of them. I going to put one in my powerwagon very shortly. The fuel system requires 48-53psi to run. There is a company that will build a harness off of the stock engine compartment harness for $700-750. You need a computer and the number off of the computer for them as well. The early jeep grand cherokee's are great for donor harnesses and computers. A freind of mine says you only need to hook up 6 wires to make the stock harness work. Which wires is the question!