Here is how almost of all of my multigame conversions come to me.  I will never convert a working original classic.  This machine was originally an Xmen cabinet.  Over the years it was converted into several games and after being stripped of all its parts it was sent to auction.  To restore this game, it required complete removal of the original painted over side art from the wood sides, a new control panel was cut and drilled.  All surfaces were filled, sanded, primed, and resanded.  The machine was painted, then new side art was installed.  All hard metal parts such as the coin door and marquee brackets were removed, sanded and repainted.  Completely new wiring, game board, power supply, and monitor were installed.  New molding was installed, new glass was installed, new locks and more. 
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Here is the finished product.  This customer chose to go with the original X-men side art, marquee art and control panel design.  I installed a 23" LED monitor and custom made the bezel around the monitor to match.  The game board chosen on this build plays 600 games, but there are other options as well.  All the artwork can also be customized to your application. Every original machine will go through this process regardless of cost, the cost of your machine will depend on the cabinet and artwork chosen.