Harness won't work. I think you need to swap most of all the external accessories, (water pump, oil pan, headers, injectors, etc). You will probably want to replace your mounts if they are worn (of course).
Covered many times. You will need to swap over the mustang's complete front dress, flywheel, harnesses, heater tubes, distributor, harmonic balancer ,oil pan, cam, and new valve springs. This is a rather. Short list as you will find many things that will need to be replaced while you are in there. Oh yeah. Screw in adapter plug for the oil filter unless you keep the explorers remote setup.