I traveled up to Keene NH today and I decided to buy a 1993 Saab 900 as a parts donor car. A friend has his shop up there and he was able to spend a lot of time with me going over lots of possibilities. He was quite generous and sold it for a scrap price of just $300.
It will be providing the front suspension, brakes, and drive shafts, and also probably the rear suspension. Also, possibly the steering wheel with airbag, and likely other useful bits like power lock solenoids, heated seat elements, wheels, etc.
The rear suspension is quite compact, and the trick will be to locate the beam axle which is needed to control the toe, etc. I will need to get the steering rack out of a '94 or newer, as it is single ended, so I can shift it into a position where the steering column is centered. This '93 model has a much longer rack unit with the steering linkage at each end. They are available for $40-50 locally.
I will possibly be cutting out large pieces of the front inner fenders that can be attached to the CarBEN chassis with the geometry intact. The distance between the outputs on the differential is about 10" - which is about half of the width of the electric motor and differential I'm considering, and the front track on CarBEN is 4-5" narrower that the 900. The drive shafts are pretty long and the each have ~9" so in theory, they have enough length to be shortened, though obviously that may limit the suspension travel.
Unfortunately, the differential is in the same case as the transmission, so no way to just put an electric motor directly on the differential.
I'll tow it home in the spring, with my brother's Tacoma and a cradle trailer.