This is turning out to be quite a puzzle. Helical cut gears would be a problem of course but the pinions on the components we see are straight cut. This is as one would expect if they were designed to be reversible.
Thinking about this a bit more, what would need to be achieved is that the driving pinion on the end of the crank would need to be at the opposite end of the block. The changes at the top end would be easy if the heads (rather than just cams) were made such that they could be swapped left to right. I'm not sure how the cams were driven but I assume gears not chains.
I know someone who does pylon racing - I'm sure there is someone in that community who has good familiarity with these engines.