I've been thinking about this problem ever since I had to slightly crank my BMW's engine the opposite way to insert a crank-locking pin.
What are the fundamental changes required to make an engine spin the other way?
Here are my thoughts:
the short-block would be unchanged since there is nothing on the crank, connecting rods or pistons that are direction-sensitive.
the cylinder head(s) may improve efficiency if reworked but the engine should still run without having to change or flip the positions of the intake and exhaust valves.
I believe new camshafts would be needed, but am unsure since it could be that the intake and exhaust camshafts just need to be swapped over (it's a bit difficult to simulate that in my head).
Firing order may have to change in order to maintain identical harmonics. If so, would it be sufficient to just flip the crankshaft around?
To clarify, I'm not interested in other auxiliaries like the alternator, water pump or power steering pump - just what needs to be engineered on the engine in order to get it to run the other way.