Charcoal grill build

[Bigg Boy]

Hello and thank you all in advance for your helpful answers.
I am in the beginning stage of 5'L x 4'D x 30"h by, 3/16" thick box style charcoal trailed grill.
What I am seeking help with is I don't know what the distance should be from the charcoal to the food grate.
My unknown plan was to layer the floor with fire brick and just dump the charcoal on the fire brick, let the burn out with each cook,
and have a clean out door to remove ash when cook is done or should I put a slide out charcoal rack If so what distance from food?
But will there be flair ups with the grease drippings on the bricks?
I don't know and I am stuck in my build. I have very little build experience.
Just would like to know, where would you guys place the charcoal rack from the meat rack?
(I do mostly fast food: jerk chicken, Jerk pork, Pork Ribs, so on)
Where would you guy cut out the door and what height for the charcoal?
(I was thinking on the rear of grill or 2 pull out draws in the front, But still what height from the meat rack?)
How many air vent would you put?
(I was gonna do one bottom vent on each corner of the cooking chamber. Like the carolina style pig cookers)

Please feel free to way in on my build.
I am attaching a few picture of a grill that I am copying the design from.

Thanks you guys in advance!!!

 

[cowboyupbbq]

What is the objective? If you cater in nyc, does it need to meet a code?

Ism not a big fan of firebrick in a trailer-I’d look at insulating or thicker steel if heat retention is a concern. The pics look like a propane grill, which is going to have different airflow than charcoal or wood.

Best jerk chicken I’ve eaten was from a horizontal drum sawed in half. Pimento wood burned down to coals. Not much distance between fire and meat in this case but way less than I’d want for direct ribs.