You can buy pre-built adaptors that are placed between the JAMMA harness and the game's pcb. They range in price depending on the game. You could likely make your own, too, if you feel like it. I'm too lazy, though. All the re-wiring is held on the finger board, though. It's removeable and doesn't damage the original board or the harness. It's not uncommon that there is also power wired into the finger board, too, because it may not be supplied properly by the JAMMA harness.