Glad the Ignition is good for you now.
Are you upgrading to disc brakes? Is this a stock MC?
I looked on MAC's and he lists the part # 1955-1957 B5A-2140-B which is correct.
Is there a part # on the MC? It is possible that you were sent the wrong one, which is my first thought.
All MC from 52-56 are the same as the 55-57 bird. (See the Interchange list attached)
There is no difference between Manual and Power brakes MC as the booster is "after" the MC so the same MC is used.
I have also attached a pic of a MC from Rockauto. That should be more like the one you have I believe.
Also an exploded view of the 55-57 MC.
Check with MAC's to be sure they sent you the right one.
BTW the 9.30 by the interchange # is the cost of the part when the interchange list was published.
1965 I think it was.