Hi Peter, I've read the 428 page and the posts on Bring-a-Trailer, these debates always fascinate me if I'm honest.
Reading the orginal BaT posting, these chassis were provided by AC to a company called Eletric Fuel Propulsion in Detroit. EFP was based in Ferndale which is somewhat in the middle of the big-3's locations, although closest to GM's old head offices at Cadillac Place. Reading between the lines I think the Cobra chassis would have been chosen because it creates a good platform to build into a prototype. I work for Ford in the UK and these prototypes would be a called a 'Mule' (or 'Buck' if it's stationary).
There seems to be some debate as to whether the chassis were actually built by AC, but then I'd question whether AC would in fact build their own chassis on site (as they didn't build their own bodies) most car companies would assemble but not fabricate, as fab'ing steel with all the cutting and grinding is quite a messy business. I'd like someone to inform me whether AC did make their own chassis. So a possible explanation is that the chassis were sourced via AC for EFP, but may never have passed through the AC premises, although pure conjecture on my part.
