So I have updates and answers and clarifications.
I called East Penn customer service and they looked up the NAPA part number of the H8 AGM The Legend battery. It is made by Clarios and not East Penn.
I asked Customer Service who sold their batteries and she said it depends on the battery. She said with the size I was looking for that O'Reilly and Sam's Club sell it. I asked how I could tell and she said to look at the Manufacturer and it should say EPM. She also mentioned that for some reason the address on the sticker will say Baltimore, MD and not PA. She assumed it was because they have a warehouse there.
So here was my big question. I asked about battery differences/quality between labels, and she said there are NO differences. They are not selling Sams Club batteries that didn't meet specifications. She said most contracts they have with different labels do not include warranty coverage and that the warranties are provided by the labels. So if we take East Penn at their word, all the H8 batteries should be the same across all labels.
So I learned more about batteries from a 10 minute call then I did with hours or Internet searches.
Oh, and the battery will state "Made in the USA".