Thanks for the shares. Volume 4 appears to be sourced from the original vinyl and contains the original tracks. The CD versions of 1 to 3 I believe differ in content to the original vinyl versions ; it sounds like some of the tracks were re-recorded with 1980s synths as the sounds are too modern for 1977 and 1979.
I have vinyl rips in MP3 , though I'm not sure about FLAC.