What kind of carb is it, a holley 1920? Go to the slantsix.org board and check out the carb info sticky in the Engine forum.
You can rebuild it yourself easy with a decent carb kit. It's just a matter of cleaning the gunk out and replacing the parts in the kit with the parts that are in the carb. Then you flip it over and use the little measuring tape to adjust the float level. There are instructions in the carb kits. It's a very simple job and there are relatively few parts in a 1bbl carb.