At this point I must mention the
Adaptist PK+MM Multi-Mount, which I used to replace the stock K-mount on my K-30 and only looked back once (when I spent a summer week in Florida and couldn't afford to take chances with the weather sealing). There has been no official word yet on whether it is compatible with the K-1.
One advantage of the Multi-Mount over the Leitax method is that it works for all Contax/Yashica lenses, not just the narrow-mount MM ones. Also, the same mount lets you use Olympus OM and Nikon F lenses too. The only problems are the reduced weather sealing and the need to clip 3 mm off of the aperture actuation lever and guard if you want to shoot at anything other than wide open (though Adaptist claims this will not affect the lens's operation with a C/Y camera).
And I'm not just saying this because I couldn't get the last base screw off of my Planar 50/1.7 to replace the mount. Speaking of which, anyone know where I can get a tiny JIS screwdriver? Phillips apparently won't cut it.