Up for sale is a used, Holley List #4609 / Ford# C9AF-9510-U carburetor for 1968 or 1969 428 Cobra Jet and Super Cobra Jet Mustang Mach 1 and possibly other Ford models. 

Carb is in very good condition but it's been sitting in a box for years - to be safe, I'd go through it and blow out all of the passages.

 From what I know, these carbs are rated at 735 cfm, have a square bore bolt pattern, vacuum secondaries, and manual choke.