There is a lot of these swaps out there, and many are done different ways. The factory PCM from an automatic truck will work fine to run the engine without the trans plugged into it, it will just have codes stored. SCT software has the capability to turn off the transmission functions in the PCM too, so talk to someone who does the tunes and see if they will do it this way. The harness seams to scare people sometimes, but really all you need is the wiring diagrams for engine controls and connector end views. Any wires for four wheel drive or any such feature you are not using can be removed. You must keep all sensors used to run the engine such as as TPS, MAP, O2, ECT, IAT, crank sensor, cam synch sensor (distributor), and outputs such as IAC, fuel injectors, etc. Not that bad to do the harness yourself, and if you make a mistake, just splice it back in. I suggest for the first one you do, remove the covering and identify the wires you want to keep with masking tape, then write the function of that circuit on the masking tape, such as TPS ground, TPS 5 volt reference, and TPS signal. Saves rework this way.
