My first attempt to buy a Pentax 67 came to nothing when I arranged for a test shoot with my local dealer, with a 160mm with internal shutter. On a tripod, of course, but it wasn't good enough for my expectations/needs.
My next exposure (without test!) came years later when I bit the mental bullet and bought a new Pentax 67 ll. Beautifully made, it was to be my last 120 format camera: I couldn't get it to give me pix without bounce, both mirror and shutter, the latter confirmed because I was shooting on a massive Gitzo with MU. You can't beat the shutter unless you do time exposures.
Sam Haskins did a show to which I was able to go, and his 6x7 slides were great; Sante D'Orazio was another guy using that camera, and even there I can see several occasions where the thing blurs on him, making Helena Christensen look a litle bit off... and that's a minor miracle of mechanical failure rather than of nature. Perhaps Pentax shutters were not all flawed, but how could one tell before purchase?
With my 500C and C/M I found the 150mm Sonnar too short for good headshots, and I had it because when I was ¡n the market, the 180mm offering wasn't being offered. Having used the Mamiya 180mm on the awful Mamiya C33 TLR (what a gas trying to handle parallax with a moving red line!) I learned to love that focal length on 6x6. It was actually a great lens, too, but struggling in an impossible context.
Rob C