RAM arrived.
The 6116 SRAM finally arrived from Hunan to the board is now fully populated. All I need now is some wires to link the jumpers so that I can experiment with the clock speeds and I'll be ready to start finishing off the new ROM. Assuming the circuit all works. The first thing to do will be to get the video output working that should happen without much fuss as the circuit is basically the same as before. Even the boot software should be too complex but after that, the interrupt handling is all new. The new board is at the bottom.