Larry ... Not sure if that is so true. A lot of homemakers did not have the plumbing to accommodate the pump model; my cousin's mother-in-law was one (where I inherited the 1968 Model J). She washed clothes in the cellar of their farm home in Central MN until the day she died in the early 1990's. She had no formal plumbing; hot and cold water had been dropped from the kitchen up above via regular garden hoses. Rinsing was done with standard, non-plumbed, double galvanized tubs. She let water out through a small drain in the floor that ran underneath the ground into the farm yard.
In all the Maytag historical data that I have, I don't find a mention of the flywheel being made as one specific version but I would guess that towards the end of production in 1983, that could be possible. The final parts list still showed both flywheels.
I would also guess that your machine had been repaired at some point. One of the easiest ways to repair these machines was to have a power unit "ready to go". The service shop would determine if the power unit was the problem and take the machine back to the shop and "swap" out units. Hence, the possibility of getting a unit with a pump flywheel AND ... possibly ... the other things you noticed (missing tooth on worm wheel, scrap of metal). Without knowing the history of the machine, it's pure speculation!! It doesn't really matter, either, as long as it functions OK!!
Sure wish I could have heard the sounds it made when it blurped its Bosco all over the floor!!!!
You're doing an excellent job, BTW. Did you remove the right angle drive yet and clean it out? Kind of messy, huh?