Hi Jim, I'm really looking forward to seeing how you do your retro! I think a heavy gauge (13 or 14 ga?) sheet metal top with a couple braces under the lathe mounting points would work well for a top. Depends on what you have lying around. I'm sure there are some who will say nothing less than 1" plate will work.
For my Denford's new home, I modified an existing 36"L X 30"W X 36"H 2x4 wood frame I had under an old homemade CNC router . I covered the top with 1x6 tongue & groove pine with the grain going across the short dimension and added some diagonal braces to stiffen it up. The T&G locked in very nice and seems to be very sturdy.
I picked up a piece of black plastic carpet runner at Lowe's and covered the top with the grooves facing down to give a smooth surface for wiping up oil spills.
I'm using the original ORAC base to mount the lathe on and house the electrical stuff. The panel across the back provides a backsplash as well. It's real stout and has 2 rails running longways on the bottom that spreads the load across the wood table top. It looks and feels plenty sturdy.
The lathe will be pretty high off the ground but I did a few dry runs and it feels pretty good actually. I have to be careful with my back and I'll try it for a while as-is when I get it running. I can always shorten it if necessary.
"Accuracy is the sum total of your compensating mistakes."
"The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton