The difference is that GM used to own Sabb, same as they own Holden in Austrailia or used to own Opel in Germany. Now if we're talking joint ventures, that'd be like putting a Subaru in a GM product, since Sabb partnered with Sabaru in the last few years while the Government Motors owned them, and share a chassis. Speaking of chassis sharing, what about Mazda and Ford, lots of chassis swapping there, Mx-6/Probe, Mazda 2/Fiestiva...