I bet the easiest way to turn it into a Centipede/Millipede is getting a 60in1 and a switching power supply. And a monitor and trackball of course....
You know with people giving away computers on craigslist I imagine the easiest way to turn it back to centipede would get a free comp off craigslist (even a 300mhz is fast enough) and use Mame. I'm sure you could also get a free 19inch monitor no problem.
Then you just need an ipac and controls and speakers. Much easier than getting a power supply and all the jamma stuff. If you really want to use a real arcade monitor get an ATI card and run that 15khz program.
Also if you use dos you can right a batch file that will boot straight into the game. I think the Mame route could be much cheaper (and more authentic that a dodgy 48-1)
I'll disagree with the "much easier" assessment. Wiring is wiring. I find wiring JAMMA with an authentic monitor to be much easier than messing about with other stuff (I haven't wired a MAME cab anything but JAMMA since my first MAME cab).
As for the computer part ... I would use a 60-in-1 (since ... doh ... the 48-in-1 doesn't support trackballs) or a Centipede-to-JAMMA converter, but same result can be achieved with a low-end PC (and if you want to interface with that PC, I would use a JPac).
As far as specifics with cost goes, I won't say much (!) since saint has asked us not to mention the price of xx-in-1 boards.
I would tend to lend some credence to the advice of Level42 ...
