Any interchangeability among HM80 engines?

Hi, All -
I'm trying to help my Amish neighbor get a replacement engine for his log splitter. The model number of his engine is HM80 155653S. I've found engines on both eBay and Craigslist that *look* comparable (e.g., a new HM80 155432M, with a 1" diameter crankshaft that's 2 and 3/4 inches long), but am not certain if this will work. Can anyone help me determine which engines are comparable (or point me to a resource that I could use)? Thanks!