Real deal or move along?

That list on Moparts is correct. It’s stickied right at the top of this forum. This version has a couple of extra widths I added as well.

An accurate 8 3/4" rear axle width list

I've seen that list posted here and over at big block molars, but the problem for me is that it starts (for a bodies) at 1966, and I'm trying to confirm information for 1964.

Perhaps during the process of swapping my axle I could take measurements of my stock axle and contribute to the common knowledge.

That still leaves me with the questions I asked in my original post.