I don't know if they'll do research in their library for you, but the RV/Motorhome Hall of Fame in Elkhart IN has a huge collection of past publications.
According to their site, they should have what you're after:
http://www.rvmhhalloffame.org/library.cfmWe were able to find this while we were there:
(which goes much further back than what you are seeking and is my first, last, and only cover shot! I'm the little girl)