Head bolts: Get the proper Grade 8 bolts, and remember that on most K-series Kohlers, there are two lengths....check the specs., and remember which holes the shorties and the long ones came from. Chase the female threads in the block with the correct tap, and blow the holes out. Be sure your head isn't warped and if it is, have it shaved (kissed), or plane it on a flat surface with #180 grit paper until the mating surface is equally frosted.
Now, if you have been having head bolts loosen (such as the front two or three), drill a .060" hole through the bolt heads. Use a new head gasket. Install them with good flat washers under the heads, and torque to spec. Run the engine 30 minutes and let it cool an hour or more. Retorque all the bolts....they may or may not tighten up a bit. Now, use .040" stainless safety wire and lockwire the bolts 2 by 2. Use safety wire pliers, or duckbills, and get that wire tight! Not sure how? Check "FAA Regulatory Guidance Library" on Google, and click on Advisory Circulars. Then find AC 43.13-1A, and you will find a picture of a proper wire job.