360 engine vibration

Hold your horses here a minute, You are over thinking this way too much. Keep it Simple.
You just need to install the new damper.

If you go back to the video you put up for us to see where you are rolling over the engine and showing us the wabble on the damper at the timing marks on the front timing chain cover. You will see that the center of your old damper hub is running true and straight, as the front pullies are running true and straight at the same time. It's the outer ring on your damper that has moved and is wobbling. The cushioning rubber between your damper hub and it's outer ring has failed, too much age on it as it is shrinking, drying up, and getting hard, after 40 years of service life. It's time to replace the damper with a new one. End of crankshaft is fine and is running straight and true.
I hope I am over thinking this, currently sat at work googling 2nd hand cranks or short blocks LOL. On a plus point I've prepared myself for the worst.

However the damper has zero wobble when in the lathe inner or outer, yes the rubber is out of position and not running true. I just dont see the same wobble or any wobble as on the engine. Yes a new one is still a good idea and on the parts list. I was convinced it was the damper but having seen it run true in the lathe it doesn't make sense therefore I need to revisit the crank as my DTI check was very crude and late at night!

I'll post back in a few hours once I've checked again. I'll leave it on that cliff hanger!