Zach. The '57 Ford dual quad intake was originally outfitted with two Holley 4000 carburetors. The Holley 4000 has the same small carb base style as the early Carter WCFB carburetor that was used on two models of 1956 Mercurys.
To mount the 1957 Carter AFB you have on a manifold with the early Holley 4000 / Carter WCFB bolt pattern you will need an adapter. Although two adapters will mount on your Ford 2x4 intake manifold, I don't know IF your two AFB carburetors will fit side by side.
IF mounting two AFBs on your intake manifold is workable, I'm sure that a Forum member has done it and can speak to it.
Here's the adapter that Speedway Motors offers for what you're looking to do...
http://www.speedwaymotors.com/Holley-Flathead-Carburetor-Adapter,5551.htmlHere's the adapter that Charlie Price's Vintage Speed offers for what you're looking to do...
http://www.parts123.com/parts123/PartFrame.asp?ZTM=cadegdha&GHOME=www.vintagespeed.com&TITLE=VINTAGE_SPEEDIF the page doesn't open for you, search on the Vintage Speed site under Category: Fuel Lines- Blocks- Carb Adapters, Page 3, Part No. FL-CA-8
Check back, others will be able to advise you further on this.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York