how can I get my hands on a copy of LIFE Magazine dated April 23,1971?Dog, your library ought to have Life magazine from that period on microfilm. It may also be on a digitized archive. As Molly Pitcher wrote, ask your reference librarian. If you can't find it, let me know, and I'll put it on my list next time I'm at the Libray of Congress, which will be in one or two weeks.
Elsewhere, there are some fabulous new resources you can use, the product of those great American traits, genuis and competition. The last century of popular magazines and newspapers are being digitized. Unfortunately, the NY Times and Wash Post have taken advantage of it, but so, also, has the Wall Street Journal. Proquest, to which your library likely subscribes, has digitized these journals from the 19th century on, and you can key-word search them with great accuracy. Try it out on Kerry. You can search via article titles (limited) or article text (expansive and will be overwhelming), but it will dig up every instance of the word "kerry."