Thanks for the response!

The group moved on to
https://groups.io/g/UCSDPascal
because the new Yahoo owner (Verizon?) decided to remove all user content in 2019.

A spidered image (from 2019) can be downloaded here
http://pascal.hansotten.com/uploads/ucsd/yahoo/files.zip
or here
http://pascal.hansotten.com/uploads/ucsd/yahoo/messages.zip
(with meta info)

Two utilites looked good - but failed on the skewed images - so i needed additional steps (see post above)

a) PSYSREAD (Delphi, with PAS source) complete with a nice GUI (Windows only?)
[included in the file dump from 2019]

b) command line utilites from Jefferson Computer Museum ('bu.exe' = UCSD burst files to disk)
[must be obtained from web site ?]