Unless you're concerned about the numbers on the mounting foot of the base, consider using a 4966S AVS carb. They were used on the luxobarge 440 engines, which were built in much bigger numbers than 340 cars...
This is not true. The 4966s AVS is the same cfm as a 340 or 383 AVS. To get the large AVS you need to find a 440 High Performance AVS such as a 4640s they run about 750 cfm as opposed to the 630 cfm of the smaller primary bore AVSs.