Re-subject'd as this part of the conversation diverges.

Found the quote that I was thinking of when I said that:

https://yarchive.net/comp/bsd.html

"Research Unix 8th Edition started from (I think) BSD 4.1c, but with enormous amounts scooped out and replaced by our own stuff." - Dennis Ritchie

The "I think" adds some murkiness for sure.  There's definitely a good chunk of code from 4BSD.  Compare init, getty, locore.c (as opposed to .s in V7 back).  Heck, even the main.c between the two kernels are more similar to each other than V7.  I would almost opt towards calling that being rebased on 4BSD rather than V7 with bits and pieces of BSD added.  I could see it being more beneficial to start with 4BSD and tack on necessary Bell bits rather than take V7/32V and try and shoehorn in the VM implementation for VAX.

The 4.1cBSD copy on the archive does appear to be pretty different, so in terms of raw comparison, I suspect the basis is 4BSD rather than 4.1cBSD.  I don't know that we have a clean copy of 4.1BSD gold, I'd be interested to see if the structure of the source code changed between 4.1 and 4.1c, as 4.1c does exhibit the new organization by the BSD folks, 4BSD still shows folders like cmd, lib, and so on.

Not trying to be combative by any means, but I've been doing a bit of research lately into when V8 was snapped from BSD and where Bell and Berkeley then diverged from that last major confluence, especially with a focus on init and other early stages of userland.