Yes - it is definitely "Blaydens Pass". This name appears, with many others on a sketch map of the Bundundah - Ettrema Area compiled by Peter Harris (NPA and SBW) in the late 70's. Peter, and other walkers he walk with like Warwick Blayden did a lot of exploratory walking in the area during that period. Also - the area was under threat from mining at Jones Creek, and there was an important conservation battle. I have not seen the map, nor been up or down the pass so cannot help with its location. I had a look through "Fitzoy Falls and Beyond" and nothing there. It is mentioned in an article in this SBW magazine from September 1993. Here is a link -
http://sbw.ozultimate.com/1993/199309.pdf (page 2), which is interesting.
Dave