Electric Food Warmer Cart conversion

I don't post much but I want to share this build and I welcome any advice. This community has always pointed me in the right direction. I came across this stainless steel insulated box. In a previous life it was a food warmer cart with a removable electronic warmer that went as high as 220. Seemed perfect to me.. Right away I imagined a firebox underneath using the existing cutout and rough terrain tires. I did my research and confirmed the insulation would handle higher temps, found out a 12" steel parts been perfectly holds a 10" steel parts bin and bingo Now the plan is basically a water smoker, possibly reverse flow of some type. The firebox is completely dependant on the Pitmaster IQ system. I will put in a defuser plate and set in some type of steel water pan. What I don't know yet is where to cut in the exhaust vent. Top, side, back? Any advice is appreciated this this five foot tall and two feet deep