750 vacuum secondary carb with some kind of rear block - the 10569 block is a 750 front block number. The rear block might be a legit conversion block or something spirited off another carb.
1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.
