I watched that video also. My motor is a 1957 and the impeller cartridge is upside down compared to the ’58 motor that he was working on. NO gasket between the center section and the gear case. I don’t remember a left hand tread on that spanner nut but maybe it was LHT. My impeller would not fit the drive shaft until I filed the key way square. Not criticizing but beware of changes from year to year.

dale