I am in the process of installing a new DS footwell to my 90. I have rebuilt a bulkhead previously, it was off the truck and I then had it galvanised. This time I am replacing the footwells in place as the rest of the bulkhead is rust free.
I coated the footwells seam/overlap areas with http://www.zingausa.com/
and then cold galv before spot welding together. I feel I have good protection within the overlap areas now to prevent future rust.
I have just sealed all of the seams on the exterior of the new footwell and I am very tempted to seal the corner seams of the interior. Being so hard to keep a truck 100% watertight, and having wet shoes at times I figure some water will make it's way into the seams at some point from the inside. So if the interior is also seam sealed it should increase the protection against any moisture getting in between the two panels at all.
Is there any disadvantages to seam sealing the inside? Has anyone done it?