I would have mamed the pee out of it. A good 19" medium res monitor costs as much as the thing would be worth working in the first place, and you can always interface the original controls and swap the panels.
Also, mamed cabinets never get converted back. We all know this.
Based on the descriptions at that website, it most likey was/is/will be mamed. I'm not entirely sure what's going on with the website though. For example, the Simpson's 4-player cab describes
Full artwork on both sides and control panel!
Newer 27" Wells Gardner Monitor, gorgeous Picture.
Newer joysticks and buttons, fully tested.
Will only increase in value !
$ 1,495.00
(Upgrade this to 1000 games for $2,495.00)
Yet right at the top of the site,
REAL Arcade machines, JAMMA arcade standard wiring, play thousands of arcade boards in these machines, THESE ARE NOT computer emulation based machines. Own the real deal at a great price, free classic game package included with your machine! Click the tab that says "games you can add" to see all of the many REAL games you can play in addition to the multi package that you will receive for free!
The only thing I can think of is he's installing XXX-in-1 boards. I don't know if I consider a Chinese XXX-in-1 board not a computer or a "genuine" arcade PCB.