There different to yam outboards & like rocky horse poo. His easiest solution is use the rh one he's just been offered and swap the cable over in the engine bay as the drives can run either way
He'll probably not even notice the difference
You can run a left handed Alfa 1 backwards all day long because both bearing sets are beefy. It used to be a cost saving that the v6 and Alpha reverse gear was inferior - I believe this was phased out and all boxes are like the counter rotating one now and can run L or R but don't quote me on it.