401 V-6: carb or Holly Avenger EFI?

Planning on dropping a 401 GMC V-6 into my Willys Overland PU.

Right now the engine has a 2bbl it ran in the New Idea harvester but I think I'll need something different for the street.

First question is how much carb do I need for 3000 rpm redline? I get a theoretical 350 cfm. Does anyone have a link to a good calculator etc. to make that a number with "higher confidence" level?

Anybody used the Avenger EFI? kinda $$$ but if it will cut lots of problems (like intake manifold, etc) it might be a good investment for a daily driver/work truck.

 

my .02 cents,, those motors were known for horrible gas mileage. less than 10 mpg.

changing carbs may help but no way would I use one for a daily type driver.

 

Why do you need a different carb?