I happen to be doing something very similar to Mark. I was gifted a large annealer that I'm rebuilding also. I had planned to replace the Omega controller on the thing once I knew everything is functional as is. My question is related to a separate plug (120v) for the controller. The design follows almost exactly Dudley's circuit shown here:
DudleysDiagram.jpg
My annealer has two plugs 120v for the controller and 240v for the elements. I assume this design was to incorporate the distance between the controller and the lehr. Is there any reason you know of, not to just tap the neutral from the 240v plug across one of the hot (in this case Red wire)?
My thought:
OnePlug.jpg
Am I missing something?