I reread the rest of this from a year ago. Some things have changed but the basic plan is still the same. Yes I will need the key, das, and ECU as a group. This is fine. This is why I bought this 97 for $400. It's the OBD2 M104 722.6 combo I wanted. It runs and drives so I can make it work but I might be hooking up extraneous parts. I'll probably spend some time unhooking stuff from the car until it stops working properly. It does seem to be a simple ABS system that doesn't need the pump or wheel sensors to be hooked up. I haven't tried unhooking the diff yet.

Before buying converters I'd probably just modify one of the R107 diffs I have and install the pickup ring and sensor. There is a small shop where I work.