Howard,
Changing that internal debug output into a real lamp output in Mame creates the proper output. As I mentioned, I verified this behavior on my actual Gorf.
The output on the board is an address latched output, the lamp drive itself coming from the Rank board just like the coin counter and rank lamp drives.
Another thing I had to do was to add a lamp output (since its a convenient digital output) to the two coin counters in code, so that I could pass the counter drive to the driver board.
Compiled Mame after adding the hiscore and GroovyMame diffs, and it's working fine.

Hoping to have this project wrapped up soon.
For clarification - my Gorf boardset had a blown IO custom, and replacements are about impossible to find.
I built a small PC running Win7 x64, on an SSD, and using ATOM_15 and CrtEmudriver. Then I built a PacDrive and iPac2 based adapter set that plugs into the harness where you'd normally connect to the Game board in the stack.
Boots in ~9sec, about the time the tube takes to warm up. It's almost indistinguishable from a real boardset.
