I suggest that you look here for Mega ST ROM upgrade with 32 pin EPROMs :
http://atari.8bitchip.info/flashest.phpIt is important that do some things with W2-W4 pads.
Text between 2 pics of Mega ST ROM upgrade:
"On pic above is how it is solved in Mega ST. 32-pin sockets are inserted in original ROM sockets, so that pins 1, 2, 31, 32 are in air. Pins 30 are cut down, and is best to put little insulator between them and sockets, to avoid contact.
Connectiing of Flash EPROMs: pin 32: +5V (Vcc) , add cer. capacitor between it and GND, with shortest possible legs.
pin 31: (/WE) /RW signal from CPU - via resistor and protection switch (explained later)
pin 30: (A17 of Flash) to selection switch
pin 2: (A16 of Flash) to A17 of CPU - it is closest at W2, point 3 .
pin 1: (A18 of Flash) to selection switch
Other connections in Mega ST: W3 (remains) on pos for 1M ROMs (2-3 connected). W2: remove shortcut and connect point 3 to pins 2 of Flash EPROMs. To point 2 of W2 connect inverted RW signal of CPU (this leads to OE pins of ROMs) .
W4: remove shortcut (if there was 6 chip TOS), Lower point (ROM2 signal) goes to selection logic, upper point comes from selection logic - then need to cut (desolder) pin 12 of 74LS11 , to avoid conflict.
"
Of course, if not using Flash EPROMs and don;t want in circuit programming, you just connect +5V to point 2 of W2 - what leads to OE pins. And another not to do is: do not cut (desolder) pin 12 of 74LS11 - it is needed if no additional logic.
Pin 31 of EPROMs go to +5V, of course.