Actually the new buyer got a great deal. A twin monitor cabinet for only $100.
One totally sweet option for it would be to install two sets of PCBS/power supplies in the game, and run one game on the top monitor and another on the bottom. This would work best with games that are only one player at a time. So player one joystick controls game one, and the player 2 stick controls game 2.
That also might be a Playchoice, my buddy has one of those.