Who's got a stand alone controller for the NAG? I've not seen or heard about it?
My understanding is the key problem with installing the NAG is that the computer relies upon wheel speed sensors to determine the speed of the car to determine what gear the car should be in, as a result you need to add speed sensors to your wheels or add them to your driveshaft.
The RFE 545 has a speed sensor built into the output shaft of the transmission which provides wheel speed, thus no additional sensors required.
As stated above I know of no standalone controller for either the NAG or the 545 if you do point me in the right direction, I'd love to read up on it.
Finally, just so your clear, many have put both the 545 and the NAG into a classic mopar, but be aware that it requires significant surgery to the floor. It is NOT a bolt in operation by any means. There's a lot of good threads on here by guys who've done it, check one out before you begin. No sense in re-inventing the wheel.
Regards,
Joe Dokes