The old tecumseh book lists #33346 as being a slanted spark arrestor taylor muffler with MTD listed as the only customer name, Its for an HS40. Does not give listings of bikes they were used on, just a customer name. It looks like MTD used a couple different styles (one at least was thier own) possibly depending on model or year made. I dont know if the part number would be stamped on it or not so that part number may not help it lists the muffler position a 5 degrees, where the 33224 is listed at 90, so that should put it up and more centered not off to the side.
None of the HS50 specific slanted headers listed in my parts book show MTD as a manufacturer that used/ordered them
remember HS40 and HS50 engines have different port configurations on the exhaust (intakes as well of course), they will cross fit, but not very well as the inlet size is different, the ports dont line up, and sealing surface gets lost.
Left HS50, center HS40, Right H25-30-35