Carb recommendation help Slant 6

Well the reason im going 4bbl my son is excited about it. He has autisim and is very detail oriented so i couldnt get away with a 2bbl if i tried. Im actually very excited as hes given up his hour of video games a day to research carbs from here and .org. I know about the edelbrock and the holley but he was also looking at something like a factory 4bb carb but he was disappointed he couldnt find something between 400-500 cfm. The holley is out of my price range new and id rather buy new or a good reman if possible. Thank you for the input.

Simple. Use the Edelbrock 500. It's an AFB. That's the same type they put on the Hyper Pack, it's just a modern version.