If you check the link above it tells you what are acceptable SRAM chips ( 2k x 8 - a 6116 SRAM IC can be used to replace it)
My layman theory is that I should replace all the caps, including the missing ones as bad power delivery could have been the cause of the other chip failing. Given I have a donor board, I already have everything I need, so I think I’m going to go for it.
Found some old stock TMM2015AP-15 Toshiba's and ordered a few.
My concern about the missing capacitors is that the funky diode on the KA51 is reverse polarity (at least it is on mine) so I don't trust that the rest of the capacitor spots are correct anymore.