Cudaman - member Darius had someone make an aluminum adapter that mounts to the back of the trans and then you can use the slip joint front. He has a big build thread over at forbbodiesonly.com Plenty of pics too.

I heard back from Russell at Sound German Automotive. He has a facebook page with more info and reviews from customers. Looking at the website, you have two programs, which you can switch on the fly. It is a little pricey and has options you can get. He quoted me about $1200 for a kit for an older car. Here is some info he sent me:

It requires a RPM, TPS value and shifter status in addition to the the supplied driveshaft speed sensor kit I supply as a minimum to operation the transmission.

It works with all year NAG1 transmissions, plus he can control some Mercedes and Porsche transmissions.