My two cents, and this likely won't have me being Mr popular today - but you should probably never upload a newly circulated tape to youtube.
Even though the taper is now deceased, the people who may have gone through great trouble to obtain and transfer the tapes may be upset that the quality has been decreased greatly on youtube so soon after it came out.
In this case there is no "don't mp3 this" clause, but there should at least be a grace period while the original seed is still hot. It took nearly 40 years for it to get out, and it's not unlikely that someone would be pissed off that it took 40 minutes for it to lose half its quality.
I'm not here to tell anyone what to do, but I just have an extreme respect for 70s tapers, and would like to think they'd want their tapes to have their quality maintained as best as possible.
Youtube is basically the new mp3. If the show didn't come out on youtube, then it probably means the people involved wanted something better for it.