Just a thought....you didn't mention which engine you were bolting the T56 onto but you might want to ask a T56 specialist about the motor and transmission mounts.
I've used the t5's behind the 235 with a front and 2 bellhousing mounts and have run the box both with and without a rear cross member. When I ran the normal 3 point motor/bell mounts the T5 was free to move as the frame flexed. With the rear transmission mount added (the 4th mounting point) I noticed that there was a binding effect as the frame flexed. The T56 is even longer than the T5 and was intended to have a rear mount (the third mounting point in a conventional engine/transmission setup).
If you're putting this behind a V8 the mounts would be conventional 3 point and it would be a non-issue. However, if behind a 235/261 you might be putting a bunch of stress on the transmission case if you used the rear T56 mount. Hopefully your transmission information source can eliminate any potential issues.
Dave
