I have this exact question. I have one with a rebuilt v4 that continues to smoke. Also I cannot find the hoof governor to replace the junk one that came with it, it's an hoof s-300 I believe. Anyway, I am curious about a different engine. It also has a torque converter. Anyone swapped engines or repowered with all hydros??? I have too much time invested to stop now. Any information is appreciated. Thank you.
I've heard about swapping with a Kubota engine but haven't done it myself. Could be worth looking into if the dimensions match up.
You might also want to check out second-hand forums, sometimes you can find parts that are not listed elsewhere.