I looked at PC0675. Keep in mind all my knowledge of the Model A comes from the PC0675, your pictures and your video. I haven't owned one long enough to make any repairs. I see it calls it a spacer with oil seal for all the serial #s.
Your picture in your post #24 shows the outside of the spacer pretty well. I also noticed it in the video. It looks like there is a ridge for some type of seal. Did you check the inside of the flywheel for a hint or inside that cover? Like a piece of some kind of gasket in there. I'm guessing the spacer had some type of cork gasket glued or pressed into it at one point. That's why it doesn't have a separate part number.
What does the inside of the cover look like? Any signs of anything rubbing in that area?
That spacer is actually an oil slinger. The groove and shape of it is designed to throw the oil away from the shaft. The cork is there to keep the oil from getting in-between the slinger and the crankshaft.
I think you may have a breather issue. There is a vacuum pump located at the rear of the fan shaft where it attaches to the governor housing. Make sure the line isn't blocked or crushed. You could have a failed pump. The idea behind the pump is pull a slight vacuum in the engine which also pulls air and oil back into the engine in areas like your crankshaft.
There's also a drain hole in the bearing housing so oil can return to the sump. Is that open and clear?
once you have installed the correct gasket, please put the flywheel back on correctly.
I fixed my leak LOL!!
Glad to hear this!
Can you elaborate on the fix? I assume you mean you set the crankshaft thrust endplay by positioning of the flywheel? Too much free-play can let the crank "wander" too far one way or the other depending on the clutch adjustment and whether or not it's engaged. If the endplay is too much, an oil leak is very possible.