Sears has many places build their stuff(the old "cheapest quote deal"). The engines aren't so much an issue as to what it is bolted to. Parts are likely unobtanium long ago. If you are handy, you can make anything for it. If not, pass on it.
I like my old Cub Cadet's. Still buy lots of new chassis parts for them all day. I've been slowly upgrading my two tractors, doing some basic maintenance/rebuilding. Decks, front axles, now freshening the old Kohler.