Hi,
Neat finds, not sure on the 64 pump, I know early 65 and later 65/66 were different, the early 65 fill was taller where the later 65/66 were short, if you look at a few 65 Gran Sports and compare the PS pump to the build date you will notice the difference, but not sure on 64, betting they all function the same, more ascetics and depending on how correct a restoration you are going for. For that matter all the 64 Skylarks I have see all look similar to a early 65 unit but never go more specific than the fill tube height.
Regards,