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