I bought a Mappy on ebay for $130 and did this to it.
New Marquee to replace the faded one $50
39:1 (hey it was free) w/ Arcade shop JAMMA adaptor
Galaga CP from Arcade Shop $28 plus hardware
Galaga CPO off of ebay for $25
Sanwa JLW joystick set to 4 way (didn't have to drill out the 2-way slot)
Happ buttons, Custom wiring straight to the JAMMA adaptor bypassing the Mappy Harness for the new CP.
All of this so that I could retain the Mappy board and CP to restore it back if needed.
I feel the flames coming on from what I did to this Mappy. Well, it's still a Namco game CP.