GE, with all of the work that you are doing on the floor it may be worth your while to pull out the interior panels and replace the insulation. When I pulled mine out I also found that the wiring had dry rotted in a number of places and needed replacement. Pulling out and putting in the roof panels is not a fun job. You can do it on your own but if you can grab another person it will help. I put mine back in on my own and do not want to have to do that again. I am glad to offer any advice that I can on the panels and windows but sadly am way to far away to offer any help. I put in a mix of fiberglass insulation along the sides and the silver foil/bubble wrap in the ceiling. You have 25 inches between the ribs except for the front most so a full length and a bit extra down the sides works fine. I found some that was the right width but it was 9 inches thick and you only have abut 2 1/2 inches of depth. Down along the bottom there is plenty of some kind of tar material used for water proofing. If I had it to do over I would pull out the entire metal floor like you instead of repairing the holes.
You have a good point if I were making a camper out of her. Since I am not converting it to a camper yet I don't see any reason to reinsulate the box yet. The floor was a necessity so I decided to tackle it ASAP. I decided to repair it the proper way instead of taking short cuts and having to redo it later!
The truck needs other work ($$$) done that is more important for me. i just bought 2 used air ride seats for the cab. I intend to reinstall the outside rails since they are coming off. They already had some screws used to replace the lose rivets. I will remove them, clean them and repaint. They will be installed with MONOBOLTS to make sure they never come off again!
There are also some devices that are mounted on the outside of the box that need to be removed and the walls patched. Since I have plenty of galvanized 24 gauge sheet metal left I will do the patching as soon as I have time after the floor is done.
I am still deciding if I will build a custom hardtop for the truck. I bought some TEREX electric wiper kits from a member. In his ad he stated that they can be easily modified to fit a M35. Based on the parts I received and the size of the hole required through the windshield I could not figure out how to use them! If I build a custom hardtop I can install the wipers through the front of the hardtop.
There are other mods I will be doing as time and money allow.
Thanks guys for all the support!