After a lot of trial and error, I finally have the basic tools working. Don't use "_" in file names and keep them to the 8.3 format. The also try to help you by embedding a jump at the start and moving the code so it will run on the CPM computer that they were targeting. To get around this, don't enable support for the linker's Intel HEX format.
Starting with a single file, I can now assemble, link, split it into the two PROMs, verify them against the original PROMS, then load the images into my old EPROM emulator. This unit supports two devices, perfect for the Fluke. I made a couple of cables to plug it into the controller board. Getting close.