Im new here so bare with me. I have a 66 GTO but have a 68 Pontiac 400 motor and have been reading on this forum some time while restoring her. I finally got motor rebuild about a month ago but I'm getting hesitation - not all the time and not at idle. She ran beautiful for about 40min last weekend then suddenly started with the hesitation. I currently have Edelbrock 600 (1406) but after researching think maybe the accelerator pump or float adjustment. I don't want to go through all that only to keep having same issues. I know y'all are thinking whatever you prefer but I also know a Pontiac is not a Ford. So I need to know from Pontiac people what they suggest....
Edelbrock carbs get bad reviews from most Pontiac guys. The only one I'd use is an Edelbrock Q-jet, which was made for them by Weber, back in the '90's thru the early 2000's. I have a 1904 E-Q-jet on my 455 bracket engine. There are usually several E-Q-jets for sale on Ebay.
But, most any GOOD, correctly rebuilt Q-jet will do.
As you probably know, a '66 GTO came with either an AFB 4-barrel, or three Roch 2-barrels. But, since you have a 400 engine with an alum intake, you are obviously not trying to make the engine '66 correct. So, I'd go with a good Q-jet.
But, if for some reason you don't like or want a Q-jet, a Quick Fuel SS-680-VS might be a good choice.