I've seen it advertised for a while too. Might be able to get a deal on it if someone was keen enough. That motor certainly doesn't look right. I dummied up a nice new quiet Honda onto my old Simplicity ride on but it just looks wrong. Maybe if that tow tractor had an office chair on the back that motor on the front might not look so bad?
Yes, I believe this machine has been re-powered - but by another Honda. My best guess is that this is a SB Mk2 Model, originally powered by a G65 Honda - c1970s