The board I googled on ksarcade looks different to the one on big daddy, obviously the reason for the huge price difference.
http://ksarcade.net/bally-say-it-again-as-2518-81.html
That one is an original board, it's the same as the one currently in my machine. The Big Daddy is a replacement board. It loos different but does the same job, it'll just mount in where the old one sits.