Thanks Ted, I will keep you posted once have have time to work on her again.

Actual compression numbers would be helpful.  Performing a leak down test would provide some additional information before actually taking the engine apart.  If the leak down test indicates 5% or less leakage, then cylinder sealing would at least be eliminated from the list of possibilities.  While performing a leak down test, do all the cylinders and not just #2 so you can get a range of values.

Assuming cylinder leakage is within acceptable limits, removing the right bank cylinder head and measuring piston to deck clearances could potentially indicate a short or bent rod or even possibly a piston with a different wrist pin location.  If the deck heights check out okay, then you may be simply dealing with an out of balance rotating assembly with an odd ball weight piston being at the top of the list.

Lorena, Texas (South of Waco)

I have mate, number 2 piston was lower than all the others. 

Have you performed a cranking compression test?

Lorena, Texas (South of Waco)

Happens when stationary and moving 

What are the actual Compression readings? High to low should be within 10% of each other.

  

Since the frame shakes, I would have guessed drive shaft balance (and possibly the yoke / u-joint) - but if it happens in neutral, then I am less apt to pick there.
It is realtively easy to pull the heads and weigh them.

At this point, everything else I can think of is a a lot of work to diagnose. For instance, you could measure the shake on the engine top while it is in the car vs. on a stand ... to isolate/debug the connection between those major system groups.


Robert  
  https://my62mercury.blogspot.com/ 

You mentioned that number 2 piston is down lower than the others. Maybe mismatched connecting rod length,
or bent connecting rod.   Try checking running compression.   Just a stab in the dark.  

Located in Harford County Maryland 

If the engine was rebuilt or throwed together with a hodgepodge of parts, then an imbalance due to a mismatch of parts would be high on the list.  If the oil pressure is good, then worn main bearings is low on the list.  Check the head casting numbers on the heads to verify that both heads are the same.  At this point, there’s also the probability that one head is milled much more than the other.  While this has likely already been performed, check the spark plug wires for having the correct firing order.  You don’t mention valve lash but that should also be double checked.

I’ll still suggest performing a compression test as that may give a better idea of where to look when the engine is torn down for examination.  While the spark plugs are out for the compression test, examine them closely for any irregularities in the color or burn patterns.

Lorena, Texas (South of Waco)