Which engine is this?

Well, by the length of the bypass hose, it's a tall deck, which means it's a 198 or a 225. There's a pad that stick out from under the head where it bolts to the block just behind and under the alternator. Probably be easier to see it if you remove the belt and pull the alternator all the way over to the passenger's side far as it will go. Then, just look right where the head meets the block just under where the alternator was. You'll probably have to scrape some grease and paint off. But it will be a series of letters and numbers with the engine size in it. Something like "RG225xxxxx" or some such.