CASCO delivered one today.

6 VOLTS/POS. GRD. NW INDIANA

If your objective is to test every carb, ignition, transmission, etc. combo/w goal of determining which combo will provide the best fuel economy, it will be a full-time job, requiring lots of parts. Conducting such tests in a controlled setting (on a dyno), probably won't be conclusive. In the real world, you have to consider traffic conditions, weather conditions (wind/temperature), road conditions, elevation, and so on. My guess would be that a 272/w stock heads, a bit more compression (zero-decking/milling), metric rings (reduced friction), Holley 390 cfm 4-bbl. carb, 1 1/2" headers, stock cam, no power steering or A/C, manual transmission/w OD, and rear axle ratio around 3.00 will be hard to beat as far as MPG is concerned. 

The “why” is because I like to tinker and I enjoy carburetors.

I have found that most articles addressing how performance is affected by changes made to any particular aspect of an engine do so exclusively at wide open throttle and typically on a dynamometer. I have never seen a carefully planned and executed “apples to apples” fuel economy comparison between different carburetors, ignition systems, transmissions, etc. and think it would be fun to try to do such a comparison myself. Perhaps I’ll end up right where I started, but I’ll have learned something along the way!

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Peeeot:  As already mentioned, I'm not sure why you want to make a change?  However, while that Ford Autolite you have was not as common in '57 as the Holley carbs, it was available. From what I've garnered from info in Y-Blk magazine & elsewhere, it's likely to give you the best fuel mileage, partly due to having  "annular" discharge nozzles above the venturies. While not more powerful, in a back to back dyno test printed in the the magazine, it was "30 percent" better than one of the other carbs in fuel consumption..         


Paul

6 VOLTS/POS. GRD. NW INDIANA

The best carburetor under the sun is only half of the equation, in my experience ignition is the bellwether ingredient. I have Taylor wires, Mallory E-Spark pointless conversion, new Mallory tach drive distributor, MSD 6A ignition box with recommended coil and a Summit 600 CFM carburetor sitting on a stock B intake. It runs like a cat in a thunderstorm.

1955 312 T-Bird Warwick, NY

Meteor, what camshaft did you install?

I bought a new Holley 465 for the Tbird a while back. I think they are not available new anymore.

I WENT FOR THE HOLLEY REFURBISHED 600CFM ON MY 292 WITH 574V DEVIDED PLENUMS.ECZ HEADS CONVERTED TO 57312 INTAK VAVES. 3.71REAR AXEL 4SPEED  4TH OD. RUNS GREAT. IN MY 1949 MERC 1/2TON. THE GUY FROM HOLLEY SEAD MOST OF THE RETURNS HAD NO ISUES,INSTALLER LEARNED AFTER THEY GOT #2 ON WARANTEE

Good point on the Holley refurbished carbs but if you DO get the email you need to jump quick.  I recently checked my email in the afternoon, found that they were back in stock, and clicked on the website to find that they were sold out again!