Rebuilding a Quadra jet is pretty basic, there are rebuild kits available from most of the suppliers. If the carb has been on the car and running not too badly about all they need is a new accelerator plunger and a clean up. The big problem with them is that the throttle shafts wear in the bore and air gets sucked into the carb below the throttle plates which messes up the idle. You can get a kit to ream out the throttle shaft bores and install bushings to tighten the shaft in the bore. I got the reaming kit from Amazon, about $50.00 CDN.