Unless your 66 is a wildly modified 289, a 650 is too big. This will be OK at wide open throttle, but give you lousy response and power at low rpm.
As for "best", I had Holleys on my daily driver for about 15 years, and having "done my time" I'm not planning to do any more Holleys. Your best choice would be an Autolite 4100. Simple, easy to set up, and reliable as an anvil.
Even Eldelbrocks usually work well right out of the box.
Summit has their own carb, based on an upgraded version of the Holley 4010. Has excellent features, many of those that make the 4100 so good, but using Holley parts for easy set-up. I have never used one personally, though, I can't comment on how well they drive.