Found a older SS fridge laying behind a business. Asked about and was told if I wanted it to take it. So I did. I gutted the inside panels, ripped out the insulation. built the bottom up 5 1/2" inches to match the opening height with 2 2x6. Then I put in vermiculite to insulate the bottom. Bought some 12 gauge stainless to remake the inside panels. got that all welded up and now shoved that box in. Before I insulate the sides back and top what should I do for a electric heating element, I have a digital controller that I will be using to control this heater with, and will be using a smoke daddy for my smoke as I do a lot of cold and hot smoke. how big of a exhaust vent should I have out the back? Other minor detail is what are ppl using for a door seal. I have a 5/8 gap to fill.