I'd be happy to send you some, well, actually most, of my cassettes. I rarely listen to them anymore, having moved on to the digital world. However, I do have two Nak decks in my home studio and I have a master cassette of set two 5/12/80 at the Boston Garden, which has some great moments. It was the only recording made front of board and doesn't circulate, as far as I know. I won't give that one up, but I'm happy to make you a copy! It was a fun show to attend.
If I could only find that one that I lost with the amazing bird song ca. 1972-3. Horrible sound quality and transcendent playing. Never did figure out the date.