Hi,
The Pentax K-mount is one of the most versatile out there. For your manual lenses you can use a K-1000, K, K2, LX, MV, MG, KX, KM, ME, MEII, P-3, P-5, P-30, ME Super, Super Program, Program Plus, MX, MV-1 and many other bodies. I think you can use it on most autofocus bodies as well. Ricoh made bodies that use the Pentax lenses, but they are not very good in my opinion. Not very strong and not very serviceable plastic parts. The K 1000 is my personal favorite and it is not hard to find. I just sold one this morning for about $100.
Thanks,
Ismael