Dang, way to rub it in Reggie. I'm over here cooking pre-made burgers and Ore-Ida fries to save time while I prep for the rain storm they call Barry. That Hurrycane better knock the power out or I'll be pissed.
Stainless will last longer. CI tends to crack and the cheaper chrome plated grates will eventually rust. You can have them custom made using 1/4" round stock and treat them like cast iron, they will season the same or close to it.
Go cheap and use expanded metal, make sure to get the smooth EP.
I'll make a point to ask him, boss. I'm kind of curious too, at least with the firebox. It WAS after the initial burn/seasoning process that I noticed, but the inside of the firebox has a glaze to it that the cook chamber does not; a shiny ceramic-looking coat. I can't imagine charcoal heat doing that to sheet steel, at least not stainless...Even then, stainless would turn a matte bluish color under high temps...
The cook chamber looks to be raw 1/8" sheet steel...
Personally I wouldn't use a pan with deep walls. The FB is small already and you need all the room you can get. I would use a cookie sheet on the bottom to catch the ashes and make a charcoal basket with expanded metal(large size holes) and make the legs about 2" to allow air to flow and ashes to fall. Something like a 10" x 10" x 6" tall should work.
The firebox and cook chamber are spot on so no worries there.
I guessed the firebox to cook chamber opening to be 3"x4" and it should be 13.82 sqin so you can make that a little bigger. Maybe 1/2" wider.
The air intake to firebox guess was a 1.5" circle and there should be 3 of them so you do need more air.
It should have a 3" exhaust 12.23" long OR a 4" exhaust 6.88" long.
Here's where you can go a different route from the calculator to get the same results.
Before I do anything I would order that 4" "L" shaped exhaust in the link and install it 4" below the top opposite from the firebox. That bigger exhaust will give you more draw and you shouldn't have to change anything else except maybe the air intake size if it doesn't work the way you like it. The exhaust has a cap so you can adjust it to change the flow and since it's a bolt on, you can easily remove it to cut it down and reweld the allthread to mount the cap back on it. All easy fixes but I would go the easy route first before I start cutting on it.
URGH. I hate to ruin your day but....... That's the problem, the firebox outlet should be at the top to let the heat roll out. The other problem is the firebox itself should be lowered to give you more cooking area. The way it is now is you have just the top rack to cook on even if you cut another hole higher in the firebox. I would drop the firebox down so the top is 5" above the bottom of the cook chamber. Weld a piece of plate 6" wide by the depth of the cook chamber about 1/4" above the firebox outlet as a heat deflector to send the heat to the side of the cook chamber and it will make the smoke rolls out and even out the cooking temps across the cooking grates. It will draw better and cook at the temps you need with a proper exhaust.
It should be a relatively easy fix, cut it off the cooking chamber and add a piece of plate to close it off. While he's doing that have him install some legs.
With these changes I would guess you should get 6-8 hours out of a basket of charcoal, run it like a drum.
Dang, another thing is the air inlet is too high, it would work better if it was lower but it may work fine with these other changes.
If you give me the measurements I'll run it on a calculator to get opening sizes. It's a little confusing to use if you haven't played with it.
Good Luck and if all else fails you can always run it using the minion method in the cook chamber but that will take some practice to get the temps right.
I need more pics of the outlet from the firebox to see what's happening.
I can tell the exhaust is small so maybe add another one to make it draw better. I would order this and install it on the side about 3" below the top, it's a bolt on after you cut the hole. While you're there order this one for the top to make it look better than the A/C duct you have.
You need an ash grate to let the charcoal burn clean and better. I would try using the minion method or maybe a basket and set it up like a drum to burn from one end to the next. Stop using wet chips, all you need is a few small chunks for all the smoke you'll need and the more you cook on it the smoke flavor will build up.
I would add 2 more shelves, one in between each rack. I'm sure that bottom rack cooks at a lower heat and is probably cooking more from the heat of the firebox metal and not the smoke rolling over it. Just guessing from the pics.
That's it for now and try to post more pics. I'll be out all day frying fish for a VA hospital benefit but I'm sure someone else will give thoughts too.