I have a 56 block with what I assume is an aftermarket adapter.  It has the thin base plate on the block with the slots on the top that is OEM ( I think), then a hard plastic ( rubber?) stepped washer, then the thick outer plate.  I assume fiber gasket on the block, then thin plate, then plastic washer, then thick plate ( with the three holes on the top side).  This is the way it was when I took it off, don't know if it leaked or not.
  I have 3 of the chrome acorn nut for the t-bird valve covers, missing 1.  Anybody have a good source?

Thanks
Paul

I dug through my stash of y blocks, and found an original spin on adapter.   Oh my gosh, was that thing on tight.  I had to use the air impact to take it off, and it was hard the whole way off.  The threads look good on it, I wonder if lock-tite was used on it.  What is the torque on the adapter nut?  Should I use anything on the nut ( lock-tite) or just put it on.

Thganks
Paul

The instruction sheet on the picture Kultulz submitted says 25 ft./lbs.