Richard makes some very good points: snip ‘ to mount the lathe on a rigid
steel plate’.
I did ask a local fabricator, and he quoted me more than $1500 dollars to
make the basic bones of a Myford lathe table and tray (square, not
hexagonal as the originals were).  That seemed a bit rich by Galoot terms.
  I then tried to find a drop of ¾” or 1” thick cold rolled plate, and my
local steel people said I had to buy a whole sheet of it, don’t have any
cut-offs available.
So,  this is why I’m here asking about concrete.   Reading about concrete.
Did you know Romans had different kinds for different purposes?  The mixed
some of the lightest, foamy, volcanic rock to make the top of the dome of a
building that’s still standing in Rome.  They used denser aggregate in the
supporting lower parts.   Hmmm.   Apparently concrete was around even
before the Romans.  How cool is that?
  Anyway, I will never learn enough about it just reading books though,
which is why I came to the Galoot knowledge base... real experience is key
to doing anything, and it takes far fewer iterations (tries, Jeff) to be
successful   if you have some good coaching...
Claudio