As I ordered a wiring harness and computer for my mustang swap I just realized I dont know how to wire it up to turn the key to start the car like normal... or do I have to buy a painless switch bored and wire it up this way to start the car? 1996 v6 auto to a 5.3 t56 swap.

 

You just have to get a schematic of the ignition switch on your car. Find power in to the switch, and find the power that comes out of the switch in the run and start positions. Shouldn't be too terribly hard to figure out with a meter.