I would consider an aftermarket harness that runs with the factory PCM/TCM at least, you will have to use the rear from the LX car if you plan on using the NAG trans- the TCM will freak on put the car in limp mode if it's not happy- my car has gone into limp from spinning then catching in 2nd gear.

They're really picky on batterys also, I threw an optima in mine and it wouldn't run because the battery temp wasn't in range or some B.S.