Paul,
I had made a resolution to add no more posts to this thread because it was getting to be a long snake indeed. I figured I'd be better off doing my homework more thoroughly and following up on the leads I've already been given. But now that you jumped in with your intriguing idea (thanks) I can't resist.
I figure my basic HP requirements would be about 20 at 1800rpm. Are you thinking, as Mike suggests, using the two front cylinders combined with the front SU? Rather than plugging the oil holes in the crankshaft, could one not just leave the bearing shells in and clamp them in place with amputated big-ends to keep the oil pressure normal?. Now that we're halving hp, what would happen if we just left the C cam in place? Let's go really wild: leave the other two pistons in, block off the intake manifold in the middle, leaving the empty carburetor mount as an air intake, and collect compressed air from the plug holes. OK, I'll stop smoking, but I would sure appreciate it if you would elaborate on what you have suggested.
Bob S.