I think you could do either, I haven't done any detail work yet but several people are heading down this route.

The easiest way would be to use the engine and box with Sierra front uprights and rear axle.

The BMW front uprights could be used in this sort of way:-


The fabrication replaces the standard strut.

At the rear I think that the easiest way to use the rear axle is to place the differential in place and make plates to suit. I don't think the suspension is suitable (none of the links are parralel to the axle line or the centreline of the car and I think the best way to proceed would be to cut the bearing carrier from the trailing arm and weld this to an upright similar to the Sierra based Roadster.

I'm hoping that between us we can sort out a very good set-up

Cheers

Chris