As muc said follow what the gasket maker says but from my experience doing the same job 3 years ago:
head gaskets & manifold to cyl head gaskets...nothing at all just clean all the old gasket material off the block & intake manifold sealing surfaces, and use a thread chaser to clean out the cyl head bolt holes in the block they will have crud in them due to raw water cooking. You also want to thread in each head bolt by hand to make sure they will thread in all the way easily.
intake gaskets, not supposed to use sealer but if your intake water ports are slightly pitted use a bit of sealer on the ports (Merc Perfect Seal, Evinrude gasket sealer or Permatex Aviation) it also helps hold the intake gaskets in place when installing the intake. The Pre Vortec gaskets don’t have the locator pins like the Vortec ones do.
Manifold to elbow gaskets do what Volvo says; I used Barr Marine exhaust on mine and the tech I spoke to said to use Permatex Aviation on the gaskets so that’s what I did. Those are the later style from what you have (actually Volvo used OMC designed exhaust from the joint venture period onward till the cat exhaust came out), and there are no small holes in the gasket that can clog on these, yours you have to be careful of these because those restricter holes must be open.
I used no Loctite anywhere but did use sealer on the manifold and elbow bolts threads and also on the cyl head bolt threads.
if your cyl head bolts are in good shape you can re use them if they are not the torque to yield type. I know the later 4.3s used these but the pre vortecs did not. I replaced mine with ARP bolts which are sone of the best made because the old ones were too corroded to clean up well.
best advice I can give is really clean clean that block deck and cyl head bolt holes well. Your heads should come back from the machine shop clean.
