Spec me out an 4'x6'x12' Oven

[Simplex78]

I have a small home-built oven that I built a few years ago that has served me well --however it is very in-efficient as to doing large quantities of work. Plus I have had to outsource a couple of larger frame pieces and would like to do those in-house too. To be more efficient, I am wanting to build a 3 foot wide x 6 foot tall by 12 foot long oven using a 3' x 5' x 10' metal rack on steel casters as a way to hang parts on. My thoughts are to preheat everything and roll it back and do the powdering and then roll it back forward into the oven for baking.

I am fortunate enough that I have 3-ph power and my plans are to anchor the walls into the concrete and use the concrete as my floor. I will probably use alumized 22 guage spot-welded to metal studs as my framework and interior wall

I have used that BTU calculator several times however I look at the results just like a mule stares at a new gate. Would someone venture to spec out what elements ...and how many they think I should purchase? Also, which controller(s) and contactors would you use?

Thanks!!