Can't answer as the the electrical, but the cable should be fairly easy to rig up. If the engine and trans are out of the car and bolted together, it would be easy to mock up, in the car, less so.

Take a look here, and you'll see their approach.

http://www.lokar.com/assets/instructions/INS0046-ChryslerKickdown.pdf

Looks like mostly off the shelf stuff.

I doubt you'd need more than 40" of cable and I'd bet a motorcycle or even a good bicycle shop could swadge the housing ends for you, once you have the length.

You can rig up a return spring and cable housing attachments that bolt to the shifter linkage bosses on the trans, or a tab that goes under one of the tail housing bolts for the cable housing. Drill a hole in the kickdown lever for the return spring to attach to. Cable housing retention at the throttle end will take a little work to sort out.

The Bouchillon setup is beefier, but not so off the shelf.