Good news and bad news on the King Lear search-
I found those two library listings on the Net you mentioned. One was for Ithaca College in New York. I gave them a call and they said they don't participate in inter-library loan programs, don't make copies, don't even allow the LP to be checked out - NADA! Stingy SOBs.
The other listing was part of a "Sullivan Collection" at MSU. Since there are five states that start with the letter "M", I assume there are five different MSUs in the U.S.. My guess is that it's Michigan State, but that's just a guess. Are you anywhere near there?
The good news is that I did manage to find at one of my local libraries a copy of Luening and Ussachevsky's other, earlier LP; taken from their historic 1952 electronics concert at New York's MOMA - a concert I suspect Welles may have been at and which probably inspired him to hire them for LEAR. Haven't had a chance to listen to it yet, but I'm hoping it's in good condition. The search goes on for the Lear suite...