Hi,
I have no experience with this but I looked at a pdf service manual and a "sure fire" way to tell would be to drop the gear cases as you would do to change the water pump impellers.
The manual shows that, looking down on the shift shaft stub protruding from the gear case, it has an indexing flat in the.splines (they call it a protrusion).
The index on the right hand rotation unit faces forward or toward the bow. The counter rotating unit has the index flat facing to the rear.
I tried to figure out how the the system is put together as to differences in hardware mounting, cable routing and control boxes but I couldn't determine that with the info I have.
As NSDON says, it looks as if most of the part numbers are the same for both types but I'm not 100% sure about that. Like I said, no experience with these outboards.
Also, the remote control parts list calls out Left and Right but no counter rotation. I believe that the left and right description is only where they mount on the hull. But not 100% sure about that either.
Sorry, that's all I can offer.
Good luck.