Trying to locate the plates is going to be a long search. just get some 1 1/2" cold drawn flat bar it is readily available
Have them cut a relief notch to clear the table and have the ends milled paralell to the sides. You will have a left and right plate as you only need to mil one side 90deg to the table face.
Then you can drill and tap any holes as needed. It is a bit of work but easier then searching for ever.
You might try Jamison Equipment in Ohio they reface the ways on those and may know of a factory set
Joe baker equipment or Farris equipment are others that may help locate some as well.
Hope it helps
Real Race Cars Don't Have Doors