ID of 351C

I just purchased a Falcon with a 351C (?) and need to identify the engine year. I am having a heck of a time finding a water pump for it. It has 2V heads but where can I go to look for a date code or something to establish a year so I can get some help at the parts store. They MUST know a car model and year before they can help. I first asked for like a 70 Galaxie water pump for a 351C but the WP they had for the Galaxie was not exactly like what I had. This is my first experience with the Cleveland so I'm new to this engine.
Thanks in advance.

I know this car is not a Mustang, but I do have two 66 Mustangs already and have gotten a lot of assistance on this site. Any help on ID of this engine or maybe a website with info that I could use would be great.

Thanks guys,

Outlaw

thanks Hack,
Everything you said is basically correct and I appreciate the info about the casting number near the starter. The problem with the water pumps was that some of the bolt holes that were not drilled in the casting on my water pump were drilled on the one from Auto Zone, and the one from AZ had undrilled bosses that I needed to bolt it up. The length of the snout was also longer. The perimeter of the WP was correct, it was just bolt hole useage that did not match up. And I did check the Mustangs as well.

Actually I found the correct pump today after viewing a picture of their water pumps. I just wanted to know the year of the engine so I would know. It is modified, to what extent I don;t know yet. It has set up for a couple of years and needs some TLC. I'm now trying to find another set of headers for the car. The ones installed or pretty rusty. I guess they were probably originally built for a Mustang. The Falcon is a 69 so I'm guessing a 67 or 68 Mustang is about the same. I think a 69 Mustang is wider between the frame rails, but I don't know that for sure.

Thanks again for the reply

Outlaw