So he asked if I had ideas about how to substitute newer memory ICs. I thought about adapting inexpensive standard read-write memories (SRAM) because a few of them would cover the Mark-8's entire 16 ...

The PIC32 “MX1” and “MX2” MCUs are the smallest and lowest-cost PIC32 microcontrollers, and are the first PIC32s to feature dedicated audio and capacitive-sensing peripherals.