Blueprinting a carburetor

I was thinking about buying a used carburetor to help keep the building cost down. Is there anything to watch out for in buying a used carburetor? I figured that a rebuild would be a good idea so I thought that I would research on how to blueprint carburetors or if this is something that is even done. Since the pure stock drag racers have to run everything factory stock that maybe I could use some of their ideas when rebuilding the 360.