The simplest method with the least amount of modification/fabricating is the Gear Vendors shortie kit that SMR sells. It's virtually a bolt in with only a small dimple in the floor pan required for speedo clearance.
http://smrtrans.tripod.com/smrtransmissionsintro/id33.htmlNext would probably be as mentioned the GM 4L60 or 4L80 with an aftermarket controller but they would require not only an engine adapter or new bell but also they are larger around in the area that goes through the torsion bar crossmember so some modifications would be needed there. A number of companies build standalone controllers for these units.
The 545RFE and it's variants would probably require the most fabrication and effort to get working. Powertrain Control Systems makes controllers and harnesses for these but there would likely be a lot of research, testing and reprogramming to get it all working right plus like the GM transmissions, they would need crossmember modification to fit as they are quite a bit larger around in this area as well.
https://www.powertraincontrolsolutions.c...ion_Controller/There's also the NAG1 transmission which is the Mercedes unit behind many 5.7 and 6.1 Hemis. Darius on the board here has a great thread on how he got one working in his car and also uses the PCS controller. I can't recall if he needed to do much modification in the crossmember area but I would suggest you go through his thread as there is a ton of good info there.
