Josh
Digging around the shop I found my old EPROM eraser, B&C Micro 1409 programmer and a bunch of 2764 and 27256 (D27256-2) proms. Tested the programmer, got a menu and found documentation on the web.
In the FIRMWARE and "CPM V-Disk Images AIR-V23.zip" archive in the ReadMe.txt I found reference to 25c256. Can I perhaps use the 27256 I found? It's about 1/2 the speed and more power hungry. Pinout looks the same.