I know this is an older thread, BUT.
I have a GM WC T5 and a Ford T5 tail shaft. Both of these transmissions were canted from the bellhousing thus giving you a 17 Degree tilt in the mount when mounted up right. There are other tailhousings out there that leave the transmission upright without a canted mount.
The Nissan and S10 are the ones I know of, there should be other across the pond in Europe as a few T5s were stock in European fords.
What I do know for a FACT, is that you can use the Ford tailhousing on the GM transmission and vise versa so long as you keep the shifter rods, forks, and top cover with the correct tailhousing.
I am waiting on my Nissan T5 to come in so that I can take a look and see what's up with it and whether I can adapt it to the GM transmission. This would be optimum for my swap.