I've a Scag Freedom Z 48" with an FR600V-AS15-R and it runs well @ 400 HRS I've acquired a Toro 74630 SS50000 TimeCutter with a blown FR651V-CS06-R with very few hours it seems. A shop told the owner it needed an engine. I can buy an engine for $1440 or so. My thoughts were to maybe use the FR600V from the Scag and buy maybe a FS651V to use on the Scag since it's a keeper. The FS651V would have a 3 YEAR Kawasaki warranty. The 50" TimeCutter should sell easily I'd think and I doubt under-powered. I'm not a small engine guy so I went to a couple shops to ask. I got shrugs and rolled eyes when asked about the possibilities. These shops I was told were "guys that knew". The only trouble that I could rationalize was potential muffler issues when mounting since both were 1" 3 5/32" (80mm) crank-shaft. I can't seem to find any engine specifications anywhere regarding mounting pattern etc. I never thought it would be as difficult to research as it's been. Can anyone see any issues that should "stand out" to tell me it can't be done? I understand there's maybe some RPM design specifications that change with the various builds of each but I can't document them. I thought I might like to use this FS651V for the Scag: KAW-FS651V-S07-S or there's many others that seem to match the crankshaft dimension. Is the crank-shaft dimension my only concern or is there a bolt pattern difference to the ZTR frame/chassis that might be different. I see no where that mentions anything other than 1/4" key-way when it's mentioned. Do they "all" have a key-way? Are some actually different? Anyone with any thoughts? Anyone know who I could contact? I've had some rather radical Cancer surgery that has made it very difficult for me to speak well and email communications with someone might be best. If I've overlooked something obvious "pile on" - I believe I can handle it. I've maybe a couple days to decide.