[mannydantyla]

What if the two engines were connected together with a planetary gear box? Might make it a lot smoother. I think that Priuses use such a thing to combine the gas and electric engines together (and it's pretty brilliant as the electric can start the gas engine, and it replace the transmissoin all together some how)

You could find a cheap open-differential rear end from a muscle car or truck. Maybe it could even be the front axle from a 4x4. Except the power would be going backwards - from the axles to the yoke. And the gears are not cut to be operated that way. Is it the same as driving in reverse though? I know that the front axle on my jeep is a "high pinion" as opposed to a low pinion, and gears are cut in reverse for this to be possible. Something to think about maybe

Of course that would add a lot of weight as they're encased in cast iron...

...and it would throw off the gearing.