Then burned it to the W27C512 EEPROM.
Then I prototyped the board with jumpers to a breadboard and tried it to see if we can at least fool the MiniPRO into thinking the 27C512 is a 82S135 (6309 read equiv).
Happy to report that it works so I’ve at least swizzled the pins in the right order! Won’t know for sure until it’s in circuit but it’s promising.