I own a P67 system and thought that some of the following may be of
interest to prospective P67 buyers:
 
1) LENSES
 
Some of the older Takumars were optically inferior to the present
"Pentax" marked lenses.  Call Pentax service in Colorado to find out
if this applies to the 55mm lens.  The latest lenses are marked SMC
Pentax 67 and have rubber focus rings.  There appear to have been
several releases of the lenses, with markings "SMC Takumar 6x7", "SMC
Pentax 6x7", "SMC Pentax 67" (latest).  I understand that the 165mm
and 200mm lenses have undergone design changes.  I don't have an
exhaustive list for the other lenses.  
The 75mm is reputed to be the dog of the series, though I don't have
one and have never used one, so take that with a mound of salt.
 
2) TTL PRISM
 
Older TTL prisms used a CdS cell which has a nasty "memory".  Make
sure that any second hand prism has the needle go to the minus
position when it is switched off (indicating a Si cell).
 
3) FILM ADVANCE
 
I have heard of several older P67's developing a film advance problem.
Mine had it and was repaired by its previous owner.  It leads to
uneven spacing between exposed frames and perhaps worse.  Check for
this.
 
4) MIRROR LOCK UP
 
Later bodies marked "6x7" (I believe all "6x7" bodies are >+-10
years old) have MLU.  All "67" bodies have MLU.
 
5) LEAF SHUTTER LENSES
 
There used to be several leaf shutter lenses.  I understand that these
older leaf shutters cannot be serviced as parts are no longer
available.  A typical example is the older 90LS.  I gather the only
current LS lens is the 165LS.

6) SOME RANDOM B&H PRICING:
   
P67   Body               $999.95
P67   Metering Prism     $439.95
35mm  f/4.5 SMC Pentax   $899.95 (fish eye, with case)
45mm  f/4   SMC Pentax   $899.95 (with case)
55mm  f/4   SMC Pentax   $899.95 (with case)
90mm  f/2.8 SMC Pentax   $599.95 
105mm f/2.4 SMC Pentax   $469.95
165mm f/2.8 SMC Pentax   $729.95
 
 
7) I have nothing to do with B&H
 
8) It's a GREAT camera system!
 
9) Good luck with your purchase!
 
10) Have an AWESOME DAY!