There are a number of places that offer rebuild services for GM Quadrajet carburetors. Finding a good rebuildable core may be an issue thought. I personally love a Quadrajet, when they are right the perform great, when they're bad they are basically junk. Not many people know or understand enough about these carbs to complete a good rebuild, those that do are getting more scarce by the day. I have only know one person who could do a correct rebuild and make it perform as it should , sadly he passed on a number of years ago.
As Jerry stated, find one for a 283 or 305 and you should be in the ball park for CFM. Don't worry to much about the secondary's as the primary side is where you spend most of your throttle time.
A quick search for Quadrajet rebuilder brought up a number of companies, some with decent reviews. Good luck.
