OK, never mind everyone I FOUND A WORK-AROUND SOLUTION, as I was out of time.
Since each PS1 board has designated blue and green plug-in leads on the board for front and rear lighting, which MTH did not use on these F3 guys for some reason, I realized - why not just hook up a 1.5v bulb to a spare plug-in prong cable and - BINGO - plug it into the green plug-in lead since forward is now reverse. Voila, works like a charm!
I'm a genius!
OK... not really, but just happy. Whew!