Concerns with the whole Kit And Kaboodle 07 rt swap;
Anti-theft key,
ABS to drive by wire logic contol problem (traction control)
ABS, stability management (yaw sensors) throttle control
Multiplexing modules ...no "handshake" no start
If I were doing the whole shebang I would do it ALL...Trans, ABS, SRS (use column, simulators in other areas), instrument cluster, Fuel pump module, (If fuel level gets too low the ECM shuts off the fuel pump to save it from overheating) a HUGE list...I would think twice about it and I am good at and really enjoy electrical work.
I would think the carb option, or the $3,000 FAST system option would be the way to go, I am thinking about this for myself as well.
Just my
Curt

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.

Codes are the result of something incorrect...not trying to be a S.A. but the secret to doing it is to make sure there are no mistakes initially. The FAST system will not control the trans. It can control the ignition and fuel system. There is a grey area that is the knock sensor control circuitry/logic. FAST will probably not control the MDS as well. I would not consider using the factory system W/O the steering column, 4 channel ABS and controller... I am not sure if chrysler uses the brake diaphram position sensor, at least uses the brake pedal switches. So maybe pedal assy's. Instrument cluster, PCM/TCM... Don't get me wrong it would be a cool set-up, just take a very long time to acomplish. The computer controls the charging system, cruise, A/C, I think it even controls the horn relay There are other companies that make wiring harnesses to make the engine/trans "work" I have not heard of a system that does it consistently/ accurately without compromises. The real problem is no-one has spent the SUBSTANTIAL time and moey to completely hack the chrysler operating systems. Look at the trans connector above the pan rail...I bet it is leaking. On mercedes (same trans) the tranny fluid can actually pump up the wires into the TCM....failure.
Realistically...my thoughts,
Use engine that you have,
get carb manifold
Get FAST XIM unit (verify standalone ignition control)
Oil pan
Engine mounts
Talk to Firm Feel about using high pressure P/S pump w/old worm gear assy.
Bolt on trans of your choice..lower cost = mechanical trans
hook up exhaust (no headers)

This gets you running and driving as cheap as possible.... Then careful shopping for steel crank, good rods, custom pistons, camshaft.

Now it is time to step up to Fuel Injection and forced induction. The EDIST system is a requirement to use the FAST fuel controller. Have carb manifold modified for injectors. Make log type manifolds for turbos..

more food for thought
Curt