I didn't. It was already JAMMA'd up with a NEO 2-slot when I bought it. The cabinet was also pretty beat up. I restored the cabinet, fixed the monitor and bought the 150-in-1 cart. So I didn't kill a Ms Pac (thought I can see why you would think Galaga, they're nigh identical)... I brought a zombie NEO back to life (or undeath, or whatever).
But I tell you what, if you're REALLY feeling that bad about it, I'll pull the NEO and jamma stuff out and sell you the cab & monitor for $100 and YOU can spend the bucks to restore it to a really nice Ms Pac.
That offer extends to anyone. C'mon, if you truly think you're superior, buy this conversion from me and convert it back. Don't criticize, man up.