I've seen a lot of talk about what engine to put into which plane, and I have a pretty good grasp as to what needs to be where, but here's my question. What is the difference in engines? For example: The O.S. 40LA. What's the difference between that and a O.S.40FX? Or a ringed vs. non ringed engine. I know how the bushing and BB engines differ, but can someone help me with the rest?

Thanks,
Ben