I have almost got everything i need to start my build full force. As stated in some of my other post, I am using a 275 gallon oil tank, according to Feldon's BBQ Pit/Smoker Build Calculator the 275 gallon tanks cooking chamber is 63,525.00 cubic in, and i need a firebox of 21,175.00 cubic in. I have found something I think may work. Its a old water tank off of a concrete truck. The metal is approx 1/8" thick. The tank is 48" long and 24" diameter. They also have another thats 28" diameter. The 24" one is approx 120 gallons, and the 28" one is approx 140 gallons. Will this work for a firebox, size wise and metal thickness wise?