I've never done this, but I would be concerned about the engine and transmission mounting system.
When you take a long inline engine, normally supported at the front and the bellhousing, and then take away the bellhousing support and move it to the rear of the transmission, it has to put a lot of bending stress on the bellhousing area. I don't know if that is a practical or theoretical problem.
I've also heard that flexplates have to be redrilled to match the stovebolt crank, and they are prone to cracking.
The cracking could also be a problem from improper centering of the adaptor system, which can be overcome with careful measurement for concentricity with the crank.
Finally, others have claimed that modern automatics don't shift at the proper rpm points to match well with the old sixes.
Again, I've not done any of this myself, so take it for whatever you feel it is worth. Not trying to discourage anyone... just a caution before you spend your money.
