The pump that doesn't fit is smaller than the one that came off.  So i think its the other way around. Was sent a 239 pump instead of the larger item. 

The picture of your timing cover is misleading as that cover does look like the ‘small’ water pump cover.  But if the new pump you have has a smaller bolt pattern, then you will need a pump for a 1955-1964 application.  Be aware that there are two pilot sizes; 5/8” and ¾” so be sure to get the water pump with the correct pilot size.  The 1963-64 pickup and truck engines did use the 3/4" pilot size originally but I now find them interspersed on other year engines simply due to the various engine swaps that have taken place.

Lorena, Texas (South of Waco)

Looks like 239 timeing cover to me which takes the small pattern pump,



  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Correct sorry...The engine number is B9AE. For some reason when identifying it last week something stuck in my head about 54-55 T-Bird engine. 

On checking again, its 59-60 cars and trucks. 

Your engine is not a T-Bird engine.  5/8" shaft = car water pump.  3/4" shaft = truck water pump.  The pump and pulley assembly will interchange but the pumps by themselves will not.



Lawrenceville, GA

Without at least dropping the pan, it can be really hard to tell which motor you've got. Let alone what it was bored to when rebuilt. But all 55 birds came with 292's. 272's are fine moors also. And beware, all y blocks with the pan and heads on are Thunderbird 312's. And ran perfect when pulled.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

My engine inst a truck engine. Its a 55 Thunderbird from what i can tell. My truck originally came with a flat head and its been changed at some point in its life. 

That should be the correct one. If it's going on a truck isn't the shaft diameter where the fan goes on larger then pass cars? They are also making new ones, I have one on mine but only time will tell how good they are.

Would this be the correct pump?

http://www.summitracing.com/int/parts/aaz-58-200/applications/?retaillocation=int

Yes, the 54 239 is a smaller. From 272 up they are generally the same. Don't know how the Merc motors played into that, or some,of the heavy trucks. But I'd say you need the 272 up pump.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ