I just purchased a Dr. Mario VS Unisystem with the intent to turn it into a Hogan's Alley game. To my surprise I found the 6 Hogan's Alley ROMs on the cabinet floor, but no PPU. Is the PPU unique to the game or are there other games that use that PPU? I will try to purchase the other game in that case instead of having two sets of Hogans Alley ROMs. Any help appreciated.

On a side note is it possible to get replacement PPUs?