yup. many were converted. I sold a nice converted cab at cax that someone bought and de-converted it.
Its one cabinet you should consider building from scratch. many gottliebs could easily be damaged by moisture. the cabinet is like pressed paper. Any water makes it swell like a compressed sponge.
back in the 90's super auctions used to truck in a load of games. to sell in SJ. One was a qbert. it was loaded in the back of the semi. when they unloaded the truck, the qbert had collapsed in on itself. it was shaken in the back to the point where it fell apart.
If you have the skills, have a cab made out of real wood, buy all the repo parts, jamma up the cabinet and put in a jrok board. With qbert cabs going north of $2k, it might be cheaper..
I dont know the build quality is any good, but this might be worth looking into. ask if it runs on jrok, has the knocker, the correct joystick(probably zero chance), also ask if the cab is made from real wood, plywood, or mdf. If mdf, I would pass on it.
ebay.com link: itm