Most who run 1/2 inch (8 AN) to the carb run 10 AN to the pump and also run a 10 AN return line from the regulator.

Keep in mind that a first class fuel system like this matched with a top notch pump and stainless braided lines and AN fittings is gonna run you more than $1k. IMO unless you are running a supercharged big block or natural at 700 HP+ or Nitrous, you probably don't need all this. A well designed 6 AN system is still gonna cost you $400+.

My basis is a '68 427 Vette, built to 450 HP and using stock 3/8 fuel system and Holley mechanical pump. No fuel problems at all, fuel system cost $150.

Good Luck, Kitz