I have a nice condition Simpsons PCB, 4 player, tested/working, will sell for $120 shipped. PM me if interested, I've seen these sell for more so get it while you can! Just trying to clear some stuff out...
It may be possible. Is your Gretzky machine monitor standard or medium res? Are the joysticks 8 way or 49 way? I'd look it up myself but I couldn't find a manual and KLOV entries are not trustworthy enough for this info.
If your cab is standard res with 8 way joysticks then adapting this board to work is fairly easy.