Hey Vic, sorry for the slow reply! Got caught up with work and getting this thing installed.
Got it all set up and working, thought I'd share a few photos of the process if others want to attempt the same. Again, big thanks to
Jsoboti for their initial writeup here — it helped me a ton. I will note, a lot of this would have been much easier if I had the camper off the truck, but I don't have a flat safe place to do that where I live currently, so all this was done with the camper still on the truck.
With this install, I knew I wanted to mount the heater in the space where the old propane heater lived, and utilize the propane box for the diesel fuel. The only thing propane was used for in the camper was for the heat system, so I opted to completely remove all of the propane plumbing.
Once all of the old propane stuff was all out of the way, it gave me a clear sense of how to route the electrical line into the old propane box, and how to get the fuel line in there as well.
I then carefully measured and marked out where I was going to drill the hole to the exterior for the heater turret. It was a bit tough getting the position just right, making sure there was enough clearance from the overhang of the camper, while also makign sure the exhaust and air intake tubes weren't going to exist right on the bed rail below. Got it dialed, and drilled a 5" hole. It was a bit tricky getting the alignment of the hole in the second layer perfectly aligned with the first, due the depth between layers of plywood, but I did my best. I ended up getting it mis-aligned by a few mm, which is less than ideal, but is hopefully fine in the long run.
In my initial query here, I was curious looking for a solution to extend the turret a bit to get me through to the exterior of the camper, and protect the plywood from the exhaust, etc. The sheet metal place right by my house was able to make me this female extension for the turret out of stainless steel, for $16 while I waited. It fit snugly in the existing turret, and I sealed it all off with a bunch of high temp silicone before sliding it in.
This is where I made one mistake! I should have mounted the heater to the turret first, attached the fuel, air intake, and exhaust, and then inserted this extension. It was a real pain getting those things all hooked up deep in that turret, but once I had a smaller micro rachet, it made things a little easier.
Once those were all hooked up, I was able to feed those all through the hole in the camper, and thankfully it all fit (mostly) well! This is where the slight mis-alignment of the holes comes into play.. in the second photo here below, you can see the edge of the turret closest to the camera isn't sitting completely flush with the plywood. I tried a few ways to get it to sit flush, and came up short. It's less than ideal, but I sealed it all well with a high temp-silicone and will keep an eye on it all to see how it holds up (along with an additional co2 monitor inside the camper!).
From there, I routed the air intake towards the cab, the exhaust out the tailgate, and was able to use one of the old holes from propane tank tiedowns to route the fuel line into the propane box. I want to keep a close eye on all of this stuff—hoping the fuel line isn't too close to the exhaust, and the air intake doesn't suck up and exhaust fumes. I think eventually it would be good to route the air intake a bit further away. For now, I simply wired the exhaust to one of the old tiedowns in my bed securely—we'll have to see how that holds up to rough roads, etc.
I hit my limit on images for this post, so I'll continue the fuel setup in the next.