Hi Olaf,
The T56 has a modular bell housing which means that the front of the gearbox combines part of the bell housing. This makes it difficult to adapt to other motors than the ones the box was designed for. There is a way arround it though. Salee Chevrolet sells a T56 with an adaptor plate bolted to the front of it that accepts a conventional bell housing. It would then just be a matter of finding a 427 bell housing with the right depth.
The clutch plate is no problem either as the T56 has a standard 26 spline input shaft.
Here is the link to the info @ Salee Chevrolet:
http://www.sallee-chevrolet.com/BorgWarner/t56pics.html
http://www.sallee-chevrolet.com/BorgWarner/bwt56.html
I've been working on a T56 box for my Cobra for a while now and I'm impressed with the construction.
Cheers