Making steady progress on the old factory sound deadener-(See previous post with great responses).  Game plan is to blast or dip this project along with some new floor pans.  Some of the original seam sealer just crumbles off with rust beneath it while much of it still really looks good and tight.  Some came out when removing the sound deadener especially around the center tunnel.  Looking forward to more great advice from all the Z experts on this great website.  I am really enjoying my project although it is going slow with family and work responsibilities taking priority.  Is the seam sealer actually between the metal flanges or is it just spread over the seams?  Not sure how the actual manufacturing process went back in 1978 but it seems that the sealant would not make for very good welding on those panels.  Thanks in advance for any helpful info and discussion, John-Lugoff, SC.

on my 72, there is sealer between the panels i dont know how they managed to do this and then spot weld without burning the sealer? i replaced the pans and sealed the outside and then did the inside with bedliner. my 2 cents

I have not removed any floor pans yet but I did clean up a few spots where the pans are seamed to the body rails and it sure looks like the sealer is between the 2 pieces of sheet metal.  The sealer certainly covers over the spot welds and looks like a lot of messy grinding to remove the sealer to access the spot welds to drill them out when I get ready to install new floor pans.  Any easier suggestions from those who have done the floor pan-frame rail replacements?  Thanks in advance, John-Lugoff, SC.

To the best of my knowledge sealer was applied after assembly. The sealer would end up between the panels if the gap wasn't very tight

 The only solution I'm aware of to pretreat the overlaps is weld-thru primer or zinc-rich primer. Theoretically, one could galvanize the overlaps with a flame (before and after welding) and just enough heat (around 420f) to rub a zinc strip on them. I doubt any of these areas would be affected by the heat. (Zinc strips are avail. at your local welding supply store.) The overlaps would probably last longer than everything else. There is also the possibility of taking your preformed floors and rails to a galvanizer before assembly. Yes, I'm obsessed with zinc. 40+ years fabricating and welding galv. steel. Zinc is still the best bang for your buck when it comes to protecting steel, especially around salt.

I have the seam sealer between panels as well. Removing it for the paint prep is nasty at best. I will butt weld all panels, then Marine Clean, then Metal Ready zinc, then POR15 the whole frame and undercarriage/interior floor, then seam seal, then tie coat prime, then water based paint, then clear coat.... whew!