1966 Commando 4 bbl Carb.

Correct me if I'm wrong, but didn't the Commando come with a Carter AFB ?
Something to keep in mind is that an Edelbrock is basically a Carter. All the factory fuel lines and linkage/kick down bolt right up, with the help of an Edelbrock Chrysler bracket #1481. Not so much with a Holley. Plus the set and forget ease of an Edelbrock, make this a no brainer. I'd go with the Ede 1405. 600cfm, manual choke, vacuum secondary. That Commando will be screaming.
But then again, its your car. :)