[comptiger5000]

I think for practical reasons, the 2 engines would have to share a common cooling system. Also, Frank brings up an excellent point on the engine sync. Running boats presents the same issue. A pair of 454s running about 3k rpm makes a lot of resonance if they're out of sync. Fortunately, computer sync systems exist.

Also, that Tiburon is very cool, but a little on the impractical side, as was the Jeep Hurricane concept (2 5.7 Hemis in a modified Wrangler).

This application would be best done as RWD. And, the best way to do it may be with a standard differential, and the 2 engines mounted 1 in front of the other, with the first engine feeding the 2nd, then to the tranny. When only using 1 engine, the front one could be de-coupled, and still maintain drive to both rear wheels. Or, if you wanted to be really fancy, they could sit side by side both feeding a custom tranny, or a normal one through a combiner box, so either one could be de-coupled, keeping the runtime balanced.