If you can find a source for it, Permatex Super 300 brush-on gasket sealer would be an excellent choice. It's a little scarce, but it's much better than the standard #3 Permatex liquid. If you remove the head bolts one at a time, and re-torque them after applying the sealer, you shouldn't have to risk upsetting the head gasket seal. A 20 gauge shotgun brass brush and a little spray brake cleaner would be a good way to clean/dry the block threads before applying the sealer to the bolts. Drain the coolant to below the level of the top of the block, of course.
Jerry
