Well heres what I got.

Its an AFB marked ECZ 9510 AA

I checked with the Carb Shops listings and its apparently the only AFB to be installed onto the 312s in 1957.

http://www.thecarburetorshop.com/Kford.htm

While its on my 57 T Bird,I believe it came from a Mercury.

If your interested contact me at

Oldmics@Yahoo.com

Back in '63 I put an AFB that came off a '57 Merc 312 on my '58 Ford 292. No idea what the model # or CFM rating was but after triming the spring on the vaccum secondaries until they opened up when the tires stopped spinning, it ran great and I never had a problem with it.

Years ago I used an AFB from a 58 332FE and it worked well on a Y-Block. I think it was a 2640S or 2660S.

Try to avoid the AFB's with the bi-metal hot idle lash-up. They have one large screw in the front and a bi-metal in the air horn.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

it should be on the flange front side, lower left area on the carb.

I have an AFB in rough but rebuildable shape. I"m not sure if its the correct unit you are seeking

Where are the numbers supposed to be on these things?I cant find any numbers on mine but it is cruddy.

Oldmics

Looking for an AFB in 400CFM model number stamped on the carb should be something like 9400, 9401, 9402... etc