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1965 Nailhead 401 water pump does not fit

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once again, I need to call on you for help with my Buick. I bought a new water pump. There is only a single option available for the 401 engine. When I got it home, I checked for fit (I thought) by looking at the bolt holes. Yup, everything lines up, and when I laid it on top of the timing case cover on a workbench, it looked fine. So.......I went ahead and turned in the core. This is not my first rodeo, so I should have known not to turn in the core until the new part was installed. But when I went to install it today, I could see from the top down view, that the pump did not mate correctly only at the point where the lower radiator hose connects to the pump. The new pump is about 3/4" longer at this point, than the timing case cover, which leaves the back of the pump with an opening that can not seal. All the pump part numbers are the same from 1962 thru 1966. I can't find an alternate part number, like without A/C, or, Manual tranny, or anything silly like that.

Anybody have any ideas?? My core is long gone, so if that's your idea....too late.

Thank you, in advance.

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Two questions.

1. How sure are you that the engine in your car is a 1965 engine and not from some other year?

2. Are you sure they sold you the right water pump for a 1965 Buick and not a mislabeled or misread catalog part?

I have not yet checked the numbers to be sure the car is "numbers Matching" or even to be certain the engine is a 401, but I believe I have narrowed down the problem. The timing case cover, which had a repair done to it, seems to be from a different year motor. All of the 1965 - 401 water pumps are the same as what I was sold. The older 1961 and 62 pumps, look like they will fit the shape that my timing cover calls for. I hope the length of the snout will fit behind the radiator.

Thanks for your reply!

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