I'll bet! A Bolens "hot rod."
Did you run the tractor much with the original engine? I'm sure there's quite a difference in pulling power with the twin.
Actually that tractor started out as an H14 with an engine that smoked. The way these rear ends are geared I don't find any difference in pulling other than it takes more to make this engine bog down under load. I just like that it is smooth and sounds really neat. If you are interested the original post on everything that I did to build this tractor is here (on another site...if that's ok to reference here, I like both sites but don't want to get in trouble here, if not admins feel free to remove that link....)