www.hotwireauto.com can convert the original motor harness to a stand alone unit that easily works in an older vehicle. Not cheap, but they have excellent Tech with someone that knows what they are doing, if an issue arises.

I'd buy the Salvage car, take everything that you need, send Hot wire the harness & whatever else they need. and upgrade your brakes. Any Mopar rear axle other then an 8 3/4 I would replace with an 8.8 Ford. Better gears, factory disc brake setup, 5 on 4 1/2" bolt pattern, and with the correct drive shaft flange, a Mopar driveshaft bolts up. Gene