Glen
The manifold used on the 1957 "E" setups was ECG 9424 D.
Could you have mistaken the "D" for a "B" on the castings identification?
The Carter carbs you have are not the factory intended original carbs for that manifold.
The longer carburator studs indicate that the intake was on a passenger car and not a Thunderbird.
A pair of thick bakeolite spacers was used under the Holly teapot carbs on the passenger cars as heat insulators to keep the carbs from boiling the fuel out.
The thick spacers necessatated the use of the longer carb mounting studs.
T Birds had a slightly different setup.
There was a dual quad setup listed for the 57 Merc which was the same as the 57 Ford that I am referring to.
The 56 setup for Mercury that used the Carter carbs is a compleatly different critter which is altogether different from the 56 Ford dual quad setup.
Hope this helps.
Oldmics