So, the smoker's done, and here are some pics. The propane tank sat for a while, but once it was cut, it just took a few weeks to finish.
I wound up using nitrogen to purge the propane tank when I cut it, and it was a nothing burger. No sparks, no nuclear explosions, no nothing. I did flip the tank upside down, and vented it from the bottom, so the nitrogen could push the heavier air out the bottom. The safety issue was well worth the cost of the nitrogen tank rental.
This is the sled, tank, and firebox prior to welding.
Smoke stack added, and doors trimmed and hinges installed. I really wanted to build this whole smoker in house, so I wound up cutting the spring handles off, and made my own. I did buy 3 horse shoes though. 2 for the lid supports, and one for the vent cap lid.
I put top racks on both sides, and added hangers for chicken or pork belly.