I built a P67 kit some years back and when I ran into a 645 system in the right situation, I purchased it and an adapter to use the P67 lenses on the 645 body. The 645 came with a 75 and 150 which are both solid performers, but having a 45, 55, 90, 135, 165 and 200 accumulated for the bigger camera had me well covered without buying a bunch of glass. The 645 covered for most duties very well and is much easier to handle than the 67, brighter viewfinder, motor drive, etc but the bigger camera was there for duty when I knew I'd be apt to be making bigger enlargements on a project.