As far as the early UNIXs go, any disk is collection of 512-byte blocks.     The filesystems either the early (what I’ll call V6) and the later (V7) don’t differ much.
The primary difference is that the later V7 had 16-bit uids and a provision for larger file systems/sizes.    The V6 file system was limited to 2^24 blocks while V7
did 2^32.

The 512 block size corresponded to the native sector size of all the DEC hardware except the RX which I think only had 128-byte sectors.    But again, we didn’t
do much with that other than write the standalone console disks for the 780 (in RT format) and I also used it to make “unix” file system disks for the BRL “LOS”
(little operating system…no time for sharing, uniprocessor system) that ran our internet routers and the IO hardware on the HEP supercomputer.