It's not a rambling post. Shamelessly, mine are though, and that's where you win!
The images shown are very underexposed, in addition to being quite fuzzy. Scanning can be almost as befuddling to unravel as faults or mis-steps with the P67 itself. There is evidence of unstable holding. Avoid handholding the Pentax 67 when you are just coming to grips with it, sorry for the pun. Invest in and use a tripod to gain the best in terms of sharpness at low shutter speeds.
If you cannot achieve correct focus easily, it is likely the dioptric correction lens attached to the eyepiece is of the wrong strength. These tiny lenses are not readily available on the used market now, and where and when they are, only the nearest correction factor is available e.g. if you need +2.5 you will only be able to find +2 correction. This is what I use on my 67 and it works fine.
Second point. The native focusing screen of the 6x7 / 67 (1969 and 1989 respectively)
is grainy and quite difficult to focus in low light, very much so with any lens of f4 or slower, and I would consider a lens of
f4.5 to be really pushing the ability to focus easily and correctly, notwithstanding the foregoing issue. Other focusing screens are available, but not necessarily brighter. To get around this requires, as the easier way, investing in a faster lens. Pentax does have an alternative 75mm, albeit with a skyhigh price tag at the moment: the
75mm f2.8AL (AL is for aspheric element) which will provide an exceptionally clear and bright viewfinder image, even with a polariser attached (which is routine for my work). I would not recommend using a polariser on any lens slower than f4 unless you have the patience of a Hindu cow.
Another area to investigate is calibration of the focusing screen. On a workbench, this calibration is done at three places around the central area of the viewfinder: central microprism, outer ring and near-outer matte area. It is usually done with the 105mm f2.4 lens using a focusing chart. If the meter coupling chain has at some stage been broken and the lens mount has been removed, after repair the lens mount must also be calibrated for correct focus, in the range of mere millimetres, any deviation of which will make focusing very challenging and unable to be compensated by stopping down to a deeper aperture.
With regard to the first query about dioptric correction lens, an optometrist may be able to fashion one for you matched to your vision. The sticking point is the lens has a fixed ring around it used to support it in the knurled ring that in turn screws onto the viewfinder. Sometimes even people with 20/20 vision encounter problems with the standard viewfinder lens: this can be a tell-tale indication of a problem with the alignment of the focusing screen, the lens mount or both.
So, there are a few things for you to check out now, starting with the viewinder eyepiece and after that, moving on to examining the focusing screen plane, and especially any evidence of tampering with the screws that hold it down. Anything more is generally best left to a service centre.
* Also
see this thread regarding the correct process for removing and replacing the TTL metering prism and lens to prevent breakage to the meter coupling chain.