The amount of data stored on 325 tapes would have been at most 58.5 gigabytes assuming 6250 encoding and single records over the length of the tape. Given the time frame I would guess that these were probably only 800 bpi and thus the max would have been 7.5 gigabytes. And probably at most half of that even assuming full tapes due to small records and all the inter record gaps. After applying modern compression techniques we are looking at less than a gig of data. You probably can't find any cute cat videos on You tube that take that little of space.
What is sad is that some minor functionary was allowed to make the recommendation to destroy this. -- Doug Ingraham PDP-8 SN 1175