2.11BSD lifted the 14-byte filename limit around patch 250 or so, when
disklabels were introduced (I think name length happened at the same time).
MAXPATHLENGTH is 256 and MAXNAMLENGTH is 63 on current 2.11BSD
It also changed to use the format of inodes and so on. I can't remember
all the details off the top of my head, but I think you should start by
checking if there is a disk label on the disk. If not, you should assume
it's the old V7 format, which was also used by 2.9 BSD. If you find a
disk label, you should assume you have the new format, which is what
2.11BSD currently use. It still uses the same identifier for file system
type.
Disk labels are usually in block 1 (talking about 512 byte blocks) and
you should have the magic number in the first four bytes for a
disklabel. For currnet 2.11BSD that is. I don't think anything was
sitting in that block of the disk before then.
Johnny