I put cruise in mine recently. I pulled the whole system off of a 89 325is.
The one I pulled was mounted to a bracket that bolts to the same bolts that hold the airbox in.

The bracket I used doesn't quite fit on both bolts, I've read that the bracket from an M42 E36 will work.
The power is routed through the distribution panel - a white panel on the left side of your steering column on the firewall.
Here is a link to a thread with all the info:
click herePage 3 has the details, look for posts by JakeB