I saw them twice three piece at one of the colleges in Worcester, Mass, he had had pretty much that exact Sunn setup in the bottom picture, don't remember which bass though, but yeah dirty as hell, a good dirty.
I caught Mountain in the 70's at (I think) De Paul Uni, in Chicago. They played in a packed gym, which by default was a lousy sounding room. So their overall sound was meh that night. It was so crowded that there was no way to get close to the stage, but I could see that Felix was on the EB. The most memorable part was seeing the gigantic L. West playing his tiny Gibson, which if memory serves, was a Les Paul Jr with a single P-90 pickup. He looked kinda comical with it, actually. We didn't stay long, with all those people stuffed into that gym it was a sweat-fest. Still, admission was only $3 so no great loss. I've always liked their music and would've loved to see them in a small club.

