I've never had a slant six opened up like that, but for the Chevy engines I've worked on, I've never done anything to the head bolts. Always put in dry and torqued to spec. The 350 is just a run-around truck that gets driven maybe once or twice a week, the 4.3L, although a daily driven work truck that I have driven 250 miles a day a few times with 196K miles on it, generally gets beat like it owes me money and it has never let me down. I've heard it's a good thing to do it, but even though I haven't, it may be a good thing to do so just as a precaution. I've never opened up anything this old (yet) so I never really thought about it and everything that I've worked on is generally junk and it didn't matter if anything broke.
