Carb size ?

if you are a cheap SOB like me, it's not a 4 barrel but the big rochester 2 barrel on pontiac/buicks had 400 cfm, I saw on once on a /6 and it ran like a scalded dog, the guy had machined the manifold to accept it, they are cheap and plentiful, I saw a company once, cant remember who it was took them and worked them to 500 cfm for circle track guys

correct me if im wrong but even used a 4 barrel manifold for the /6 is 200 bucks
plus the cost of the carb

as mentioned as well is the prohibitively high cost of the 390 over 300 now

power wagon you are right but I cant remember the last time I saw a WCFB

another possibility is the Rochester 4 jet they came in a variety of cfm's