Quote Originally Posted by Elox
If you get a manual K-mount like the K1000, KX or the various other all manual K-mounts (Ricoh, Chinon, Vivitar) ANY k-mount lens (non-autofocus)) will work on ANY of the bodies. I have K-mount bodies from Ricoh, Pentax and Chinon and lens from all of those makers plus Kiron and Vivitar and all work interchangeable. The problems come in when you are using program or aperture-priority bodies and them you need the proper K-mount variation.
I think you mean shutter-priority. The earliest K bayonet lenses will give aperture priority on a suitable body but they can't give program or shutter priority because they lack the extra coupling found on the KA series lenses.