Ya, I took the plastic piece off and from the top of the steel divider, the new ceiling lines up with the three shelves in the headliner. I cut some white Masonite to fit the new ceiling dimensions, then glued birch 1x4's to the top of it (so there are no screws showing from below). A layer of Dynomat, two layers of foil insulation and another piece of white Masonite for the top that is screwed to the 1x4s The back end of the ceiling is screwed to the top of the partition, the front and sides are not attached and are sitting on rubber weather stripping for a couple of reasons, I know the body is going to flex some and I didn't want to screw into anything that would show if I ever took it out
For the partition wall, I used white Masonite and cut a couple of pieces to cover the holes in the partition then cut 1x4's and screwed them in from the ends. Dynomat, insulation and another layer of Masonite. I put the 1x4s where I knew my BoBo wire rack would be mounted. Then I cut a few pieces of Masonite into the corners to finish sealing the cab up. I used some 2x2 aluminum "L" to finish the corners off and cover up the fact that I'm not a carpenter
In 15 degree weather, the cab heats up in minutes and you can barely hear anything from the back. It took more time to figure it out than it did to do it.
You might be interested in my pipe rack. I had some 10"x4" wireway left over from a job so I used 10' of it on the floor, cut through the partition and extended it under the drivers seat to carry 10' conduit inside. I put Dynomat on it also. For scrap conduit I used a 5' section of the same wire way and installed it on top of the longer one. I put a hinged cover on the end to remove short pieces of conduit that will get stuck at the end of it
It's been great so far, the Nissan service guys were even impressed