IMO, most of the Lawn-boy consumer units after the late 1960's were, well, consumer units. The cast decks were light and some of them literally crumbled apart. For all I know, the issues were metallugy, not design, but all the same...Those commercial units were better.
I just never get excited about anything that uses a design that is "optomised" for its intended use. Including Lawn Boy: later units just barely stout enough to withstand the load, with non-adjustable throttles/governors, and they just look "cheap" under the cowlings.
When I was a kid, one of my friends and I built a go-devil (mini-bike) using a Jacobsen lawnmower engine for power. We got a lot of ideas from a motored bicycle my uncle had made using a 1950's Lawn boy engine. During those years, lawn equipment engines were still more along the lines of multi-purpose industrial powerplants adaptable to anything and everything...on a lawnmower. That Jake mower's deck broke when my sister tried mowing a rock, but the motor ran our mini-bike for a long time after that.
Those designs lasted into the early 1980's with commercial equipment. Suzuki and Kawasaki, and I think Kioritzu (Echo) all made small two-strokes that could be adapted to lawnmowers. The OPE distributorship I was employed by in the 1980's sold Gilson, Jacobsen, Ariens, and Skags with two-strokes, but the only mowers Gilson sold had a little Techumseh. They were cheap, and the decks rotted out about the time the motor bit the dust.
I imagine some of those heavy commercial Skags and Jakes are running today. Ariens didn't push their walk-behind equipment at all, and I don't remember ever selling any. I think they were under-appreciated for their tractors, however. The Allis-Chalmers dealers sold lots of them, but we had a hard time breaking into that market with Ariens...but I digress.