Do these 8-3/4 rear end markings look factory? This is a ‘70 cuda, hamtramck 340 car that’s never been fully restored, so the underside hasn’t been messed with much. I’ve been looking around and seen references to the “FE” on a ‘70 challenger rear and also the plus with the circle, but not the “A” on the left.

Thanks!

For reference, here's another "FE" marking picture I found on this site, but the paint isn't nearly as heavy.

F = 1970 maybe?

Yes. F is 1970 and E is E Body.