as i stated in my previous post, pentax sells a factory adapter for mounting m42 lenses onto the k-mount body... every pentax lens that's ever been made will bolt right up to the new pentax bodies:
PENTAX K-Bayonet (external) Mount / PENTAX 42mm (universal) Screw-thread (internal) mount
Permits use of PENTAX “S” screwmount lenses on PENTAX K-Bayonet camera bodies.
Manual lens operation only
Aperture-Priority maintained
http://www.pentaxwebstore.com/detail/PTX+30120