If mileage means ECONOMY (ie including the price of the carb) I'd say the winner is the 2 carbs that you get the best deal on (one for a spare). In all my testing on the 250-pg-308 car, unheated Clifford, it was really close between the Holley 390cfm and 450cfm, the Carterbrock 600-625cfm, and the Autolite 4100 440-500cfm carbs. The Carterbrocks surprised me as they were way too big but ran within <.1 and <.5mph of the Holley's best run. I wonder if the little 500cfm Carterbrock would've won but didnt have one to include.
Overall for our mild weather as U say, doesnt make a big diff. My go-to carb was/is the 390 Holley, couldnt go too wrong there. But for everyday use, I run an Autolite 4100 (eg right now). Advantage to those is you can always resell em to the Galaxie/Mustang folks.
So it really comes down to the best deal U can get on a good runner. Good to have a spare anyway.
