For 1966 Ford used two different Autolite 1100 carbs for 6 cyl engines:
One was for the auto trans (used dual diaphrams)
One was for the Manual trans (used single diaphram)
For 66 both used the SCV (spark control valve), starting in
68 they eliminated the SCV and changed the distributor.
As mentioned get us the stamping number off the tag or
foot of the carb by the mounting stud.