Sorry to say, but those cars turn into a money pit REAL FAST!
And im specifically talking about E24's. Im assuming you are one of the lucky ones who's very mechanically inclined and has the patience to want a project like this. One major player you will need in your corner is a place that specializes in old discontinued BMW parts. I tried to do the junk yard pulls when I was doing my project but found I ended up replacing the same part again after a while which was frustrating. Therefore I decided to start replacing parts on my project car with new. The best one ive found was this place which will save you time trying to obtain parts as they were the only place I found that had it all and I mean they have EVERYTHING for old discontinued BMW's!
http://www.bmwmobiletradition-online.com/