Are you certain it's an AFB? Not that you don't know the difference, but many people see the word "Carter" and assume it's an AFB because that's the carb that Carter is known for. When GM started building the Quadrajet, the Rochester factory wasn't able to keep up with the demand. GM subcontracted to Carter to build a huge number of Quadrajets in order to meet the production needs. These Quadrajets say "Carter" on them, yet they take a "Rochester" Quadrajet carb kit. Make sure you do indeed have a square bore versus a spreadbore, to know that it's an AFB.
Just a thought...
When the only tool in your toolbox is a hammer, you tend to see every problem as a nail.