I picked up new 74LS06 chips and built one to handle the bad circuits on the Channel Address In lines. Some quick construction and wiring got it into the SAC Interface box, ready for testing. Indeed, the three bits now worked properly.
In the process of wiring it in and testing, I broke off one wire (Channel Data In bit 15) and seem to have disrupted another of the address lines. I don't have the time tonight to chase it down and frankly, the driver circuits have become so ratty, patched upon patches and extended, that I may be permanently spiraling down with each diagnostic run or fix breaking something else.
Time to build an entirely new single board for the 41 driver signals, carefully wiring the fpga and 1131 signal lines to the new board to get me to a clean new base from which I can verify functionality. I just don't trust the shoddy mess the current instantiation has become.
I have all the parts in house to do this, but it will take several hours of careful work. Meanwhile, I am working with the Ztex board maker to guide me on the problem I am having writing the fpga bitstream to the onboard flash. He has suggested a reasonable step, using one of the example programs included with the SDK because this makes use of the flash chip.