My drool Snapper is one I have two of. The Commercial with the Kawi FJ180V engine. King of ALL push mowers, end of message. Other great engines as Snapper always put on top of the line engines back in the day.
I have a Commercial with the Commercial Honda GXV160. Great mower, engine lacks cutting torque but great engine though if you cut often. If you let it get high it will bog fast.
Way back, the Briggs 4 horse L-head. Can't kill one of those suckers. I have a 1989 version. Oil stays clean like it came out of the bottle after two years of mowing and not changing. Rings are still perfectly sealed. Not bad from an aluminum bore engine. Got this one from a Snapper friend that killed a great Wisconsin Robin pusher engine. Briggs is still perfect.
Snapper made so many cool mowers. I recall that 3.5hp Briggs with the air filter HOSE. Was routed to the lower push bar to keep the air filter out of the dirt. Air filter on the push bar, not on the engine.