Thanks for the tips, guys.

First of all I carefully lowered the logic board to relieve any stress I had induced in trying to remove it the wrong way.

I checked the edges of the logic board for any notches (if I understand correctly) but both edges are straight corner to corner with no notches--at least on this board.

I looked closely at those metal wings. The wing on the same side as the analog board had clearly been slightly mangled previously no doubt to install the modified logic board back in the day. So I just carefully bent that same wing outward just enough to release that edge of the board and then was able to remove it.