V6 valve job

Decided to do a valve job on my high mile 86 SE. Not nearly as much fun as I
used to have doing conventional muscle cars years ago..wires everywhere and
sheesh, how many brackets can one little motor have? Decided to change water
pump too..sigh. The cylinders & pistons still look pretty good nary a sign
of any significant ridge in the bores and not too carboned up. I'm thinking
it's a good idea to chase the head bolt threads with a tap to clean them
out, anyone know the thread size out there? Both the factory and Haynes
manuals call for a GM sealer on the head bolts, anyone know the equivalent
commercial item?
Thanks,
Mark