Having followed both bands for numerous decades, in addition to being the author of The Association's biography ('Cherish'), I've never seen any photographic evidence of their shows together. They were on a brief 4-date tour during 1966, and at least one other occasion during the 80s (thinking off the top of my head) but despite being the two premier west-coast harmony bands of that era they surprisngly spent little time in each other's company. I asked Jules Alexander about this today and he could offer little recollection on the two bands working together... although he did seem to recall at least one other show, possibly during the early 70s, when they were appearing at the same venue...
Thanks! And it’s a bummer my top 2 bands with no evidence together. And I’ll be getting your book soon!