Looks like Milodon 21591 might have it.
The MoPar pn is 2084 355
I think it's called an oil pickup seal, even though the pickup itself screws into the block I think this O ring seals the passage from the pickup to the pump rotors.
Unfortunately, I got rid of all my B/RB stuff a long time ago so I can't measure anything out for you.
Yes, the Milodon is it. All I can say is thanks for taking the slack of my laziness. I did search Summit earlier, but just didn't drill down correctly. I started from scratch and this came up.
