If you have not already found a T56 you should consider just buying a BRAND NEW T-56 Magnum. I looked at GM Spec T-56 from Camaros as well as Viper transmissions. The Viper trans was always expensive. I was looking at $800 to $1200 plus another $1200 or so in parts and labor to upgrade an rebuild. You can get a new T-56 Magnum with a choice of gearing for about $2900, not much more then buying and rebuilding a used one. (maybe less in some cases.)

I have a lot of info on this swap on a small block MOPAR (im putting a 408 Stroker into a 56 Dodge) but can't help much on the torsion bar/cross member issues you are facing with a B-Body. I even have an unused Quicktime LA Small Block to T56 bell-housing left over.

One more lesson learned, I was able to buy a COMPLETE kit from American Powertrain for about the same price as sourcing all the parts myself. So shop carefully, do your research and decide what is the best route for you. American Powertrain's customer support is beyond excellent and I was able to get support at odd hours.

If you go down this road consider the Ford spec T-56 instead of the GM spec. The Ford input shaft is about 1" shorter than the GM so the bell housing will be shorter and the shifter not as far back in the car when it is done.

Good Luck
Scott