Any details? Don't leave us hanging like that... 
Ok, it will be
Celeron 400 (more than enough for what it will run).
I-Pac
Ms. Pac/Galaga replacement sticks,
14" VGA monitor decased and mounted to the original monitor frame/rails.
MSDOS
Gamelauncher.
The game list will consist ONLY of games that are vertical, support cocktail mode, and will control correctly with a 4-way joystick and single button (which is 60-80 unique titles I believe, I haven't checked to get the exact number yet). No clones installed except for a couple of exceptions (which will largely be installed instead of the originals, which can be done by putting the files for both the original and clone inside a single archive with the name of the clone game).
Examples of substitutions/clones worth doing (which you may also want to implement on your own machine).
Pac-Man instead of Puck-Man
Both Rapid fire and standard Galaga
Centuri version of Pleiades rather than the Tehkan version (Centuri version lets you fire multiple shots, while the Tehkan version was one shot at a time, Centuri version is also what most US gamers will have originally played).
Stern version of "The End" which is much more playable than the "original" version.