Will, on your local system, take the tarball and pull off Joy's tar binary then move it over using dd and the trick with the disks. Joy's label told you to use his program. So try it. By
on you mac:
tar xvf 2bsd.tar tar src/tar <-- the later one because he gave you two
ls -l tar <-- you may want a byte and block count
dd if=tar of=ucbtar bs=1b conv=sync <-- pad to disk block size
then on simh: att ucbtar to the rk05
and attach your tape 2bsd.tar like you did before
on v7: dd if=/dev/rrkN of=ucbtar bs=1 <-- this should pull the binary with the padded last block in
if you want to strip off the extra bytes, feel free but I don't think it's going to matter.
chmod 755 ucbtar
./ucbtar vt0 <--- see it works
If that fails, try the other tar he left you on the tape.
My guess is that the tarball Warren has was written with a more modern tar and the old tar can not handle the tar threaded tape directory. This is possible as a lot was added to later versions tars and it's clear this is not exactly the tape image that Joy wrote/distributed. So, Ken's original version might just be unable to handle it. Hopefully, it is the contents, but it was not written with Joy's 'tarit' script and maybe not on a V7/2BSD system.
Clem