Exit and Select can be wired to any unused ports. It doesn't matter how they are labeled on the IPAC - just map them to the correct keyboard inputs (ESC, Enter, etc.). Same thing goes for the pinball buttons. For the MS Pacman joystick (4-way I assume), you can wire it to the same ports as your P1 joystick - so the 4-way and P1 joysticks will use the same keyboard inputs.