I would highly recommend getting the correct plate. I tried to do it with the original plate and it ended up being just as much of a hassle.
Here are some shots from when I did it:

What needed to be cut off:

Initial placement of the motor:


Only 2 of the bolts go in after an hour or so of hacking with the dremmel:

It seems like it would be a huge pita, but go to a yard and pull the electric bracket. I went to a yard and went about pulling the old one as a means of learning how to do it without destroying my headliner. I'm very glad I did.
I just found the thread on E30tech on this. If you go to page 2 you can see my responses and how much better it is to do with the correct bracket.
http://www.e30tech.com/forum/showthread.php?t=44036