Trans-axle w/ Posi??

This may not be the appropriate place to post this thread, but I thought perhaps people who stay up on the new concepts might know about some old ones. I have an idea to put a trans-axle with something like a posi-lock (if such a thing exists) in a Pontiac Fiero. For you buffs, you know that this is a mid-engine. It is a front-wheel-drive setup, only mounted in the rear. If I can ever get the chevy 350 mounted in there how I want ($$ issue, I know there are kits out there for this), I think this could be a killer car for racing; I just need to be able to lock the axles in. If anyone knows about such a creature (the Trans-axle that is), whether it exists, could or could not exist or whatever, please let me know. A five or six speed would be awesome in there.