[rotorwrench]

Welcome to the world of Dana/Spicer 44 rear axles. The seals changed several times from the earlier Dana 41 up into the late 50s. All the modern ones use the late type seal. I found out the differences like everyone else did. I researched them and found suppliers for the type you likely have but it's been a long time since I did that research They can be converted but it is more complicated due to the other parts involved that have to be changed as well. I'll see if I can come up with a source but it may take a while.

Dana 45 was a Mercury thing for a few years since it was a bit heavier duty. No Dana 46 that I've ever heard of. Dana 53 was Lincoln for a long time but they aren't common. Bearing parts interchange between these models to some extent but it also takes research to find what will work with what.

In 1957 the 9-inch came out and replaced all the Ford and Mercury axles. Pickups kept the Dana 44 for many more years.