I went to the archive.org site and found all the tapes, but most of them are not labeled and aren't divided up; they're just massive recordings of varying lengths, some over an hour long.
The only one on the page which I was able to determine had been positively identified was a tape called "Heavy Cream" which three commenters determined (and I confirmed for myself with a playthrough) was a cassette recording of the Cream compilation "Heavy Cream", which went out of print after its first pressings from 1972-1976 (barring an incredibly brief second pressing).
I'll probably start going through the tapes this evening/this weekend, to see if anything is in there, but it could take quite a while.