To upgrade a 4 player Arcade1Up machine like NBA Jam, Golden Axe, TMNT etc with a Pandoras Box please see the below parts list:
https://www.diyretroarcade.com/collections/arcade-parts-full-kits/products/pandoras-box-saga-516-in-1-vertical-3000-in-1-horizontal-all-in-one-kit-for-arcade1up-extras (HORIZONTAL OPTION)
https://www.diyretroarcade.com/products/genuine-sanwa-jlf-tp-8yt-5-pin-joystick (x2)
https://www.diyretroarcade.com/collections/arcade-parts-control-panels/products/one-piece-design-28mm-concave-buttons-switch-for-arcade1up (as needed, we suggest 6 buttons per player to be able to play all games)
https://www.diyretroarcade.com/products/3a-pandoras-box-game-pad-conveter-to-use-4-players-on-pandoras-box (adds player 3/4 inputs)
https://www.diyretroarcade.com/products/easy-pandoras-family-pcb-encoder-plug-and-play-install-kit (easy install for player 3/4)
https://www.diyretroarcade.com/products/hdmi-vga-dvi-audio-lcd-driver-board-compatible-with-arcade1up-monitors (if using the A1U LCD, provides hdmi input)
If you have any questions please feel free to reach out.