1964 426 mystery carb

[beezwax]

Im looking for more info on a carb that i acquired. It is a Holley carb, and according to Holley tech it is an 860 cfm. It is 4160 vacuum secondary. Its currently a dual feed setup and was told that could be its original configuration. The part number on the choke horn is 2592035 and the list number is 2973. The date code is 465 which i belive translates to 5th week of june 1964. Holley listing says it was for a 1964 426 hi-perf motor. my question is, which 426? Was this carb originally single or dual feed? Is it possible its from a nascar hemi since its single four? Im having a hard time tracking any conclusive info. Any info would be appreciated.