Being that the motor is out to 438 CID, you should be able to use a carb from a 440 if you want to stay stock looking. Although I don't think an AVS, even modified, will flow enough CFM to run your motor at higher RPM's. A Holley 750 dual feed, double pump carb is pretty easy to come by in decent used condition. I would start there. Then again, it won't look totally stock.