Montg(omery?) — I know exactly that feeling of "Wha? Where have I been? This stuff is great!" I first experienced Mulligan with Baker twelve years ago, and it's now been a long-standing affair. Those two, though they may not have gotten along so charmingly, had an almost telepathic kinship. I think you'll really like the Mosaic Select, especially the "Reunion" session that includes Henry Grimes.
When/if you decide to delve further into "West Coast" material, you might also like:
• Gerry Mulligan Concert Jazz Band (Mosaic)
• Gerry Mulligan Sextet (availalbe through Fresh Sounds, or in pricier but better sounding Japanese editions)
• Bob Gordon/Jack Montrose (Fresh Sounds or the old West Coast Classics edition)
• Jon Eardley (the now OOP stuff on OJC/Concord)
... and, of course, much more. Mostly, enjoy the adventure! An enormous amount of good music came out of California at that time.