Got a good running 3 hp briggs on my Arco, does great job, geared 13-72, will top out at 30 mph, but have noticed that when start in the garage, the smell and fumes are outrageous, no smoke just carbon monoxide,=nasty= this tells me the old dude(flathead) is pretty inefficient, although not a environment fanatic, I think will go with a predator, just to be a goodguy, gearing and setup will all be the same, probly mess with governor so will still go bout same speed, but I'd feel like it was a more efficient setup, and if someone wanted to buy as original, would swap engine back, or sell with the Pred, and that's what I'm thinking at this time 
ut: I would not rely on your previous thinking at all :wink: :laugh: