Both of the 2bsd tapes you found are from the days when Berkeley just sent patches to the 7th Edition out. The 2.8BSD tape was the first one to have a kernel that was bootable from the tape. The 2BSD tapes originally had 2 files on them. The first one was a binary copy of tar that ran on V7. The second was a tarball of all the rest. As you discovered, they shipped with a label like:

Second Berkeley Software Tape
May 10, 1979 TAR 800BPI

%dd if=/dev/mt0 bs=1b skip=1 of=tar
%chmod 755 tar
% tar x

10000 blocks

but the 2bsd.tar.gz file has just the second file.

The spensor_2bsd.tar.gz has a tar binary in it:

tar tvf spencer_2bsd.tar.gz | head

-rw-r--r-- 0 0 0 24688 Feb 17 1980 tar

-rw-r--r-- 0 0 10 3687 Feb 17 1980 tar.1

-rw-r--r-- 0 0 10 456 Feb 17 1980 tar.ms

-rw-r--r-- 0 0 10 15216 Feb 17 1980 install.ms

if you are looking for that pre-built. If you are looking to create a tape with tar on it to extract other tar tapes, you'd need to use a variation on the maketape.pl with a block size of 1 so the above dd will work on the target system...

Warner