You may not get much info on a T56 in a BDR, as far as I know, mine is the only street car equipped with one. If you are using the aft shifter location, the center of the shifter cutout is 19 1/4" forward of the aft vertical wall of the cockpit.
Installing it, I would leave the shifter off, tape up the opening to keep things clean, start small on the opening, and open it up just enough to install the shifter while the tranny is in place. Also make sure you driveshaft is short enough to be able to be removed with the tranny in place (the T56 has a longer housing than a T5) The first time I removed my tranny, I had to cut the driveshaft in half, no fun at all.
Let me know if you need pictures of anything.
Good Luck,
Richard Bailey
RTBBailey@MSN.COM