I went through this with my build . I even went so far as to purchase a Carter , Holley , NAPA and Edelbrock . All of them had either 1/4" or 5/16 inlet and outlet except for the Edelbrock which had 3/8" in/out . So that's what Im' using .
Edelbrock recommends no more than 6# and says set your regulator at 5.5. As long as that's what the pump put out you are golden. Always check it though.