Oh man, that's a great Mayall album (I've got it on vinyl), but the one I really prefer is his "Jazz Blues Fusion" which came out a year or two prior. It's live too, and the songs are more intense (to me anyway). One of my all time fave albums - one of those that I memorized every note of every instrument in all the solos just from playing it a million times.
A few years ago I was browsing through a shop in Cleveland and spotted a CD version of "JBF" and bought it on the spot. Didn't even know that it'd made it to a CD version, and I don't know if it's still available that way now. But I'm glad I got it when I did - my record was worn out long ago.
That same day I also bought "Johnny Winter And... Live" and Edgar Winter's "Roadhouse" live albums too. Talk about a blast from the past!
Other discontinued stuff? I don't know... I'd kind of like to see a CD version of a Beatles LP I've got - "Oldies But Goodies" but I doubt that'll ever happen. There's many more too, just can't think of them now.