Originally Posted by
Bennett20200
I think it depends on the condition of the second Tecumseh engine. If it's low hours and seems to run well then I would just use that one. You know it will hook right up and you won't have to bother toying around with clutches and shafts. Plus you'll have a parts motor. If it's in poor shape, or you just enjoy the challenge of fitting in a new engine, then maybe I would take a look at replacing it. Just keep in mind that you need to choose an engine with the same size shaft for the clutch, or pay out for a new primary clutch that will fit with your current set up.
As for the quad motors, don't try that route. They do make more power, but they also 1) make a lot more heat which will be very difficult to vent off and 2) They rev too high, you can't spin an Argo transmission over that quickly without destroying it. I wouldn't run much past 3600 RPM through the trans, let alone the rest of the chain drive system. Those are just my thoughts though, someone else may have a different opinion on it. I'd love to see some photo's of your 78 if you have any!