The metal floor pans would have had some kind of coating on them. There was usually some sort of sprayed on stuff similar to undercoating on the trans tunnel, also.The other places you mentioned will be bonded together. Remember, these cars were made up of several parts glued together.
You can install your insulation over the top of all of this...it won't effect it at all. Don't try to remove the bonding adhesive("bondo") at the junctions...it may look sloppy, but it's there to hold the pieces together. Just vacuum it up nice, and lay the dynamat down...make sure to seal all of the edges & where the pieces overlap/fit together.
______________
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"