So I drive a tow truck. I was delivering a tool box to a guys house and noticed his neighbor selling this smoker. I got it and a propane kenmore smoker for $10. The firebox and support legs are badly rusted out on this and will not be used. But the cook chamber is in great shape and is exactly what im looking for. I want to combine this cook chamber and my current char griller together and make a custom made firebox. (All in inches) The dimensions of the vertical are H - 36, W - 16, L - 17. The dimensions of the round are Diameter - 21, W - 30. According to Feldons calculator the vertical has a cook chamber of 9792 cu in and needs a firebox that is 3264 cu in. The round chamber is 10385 cu in and needs a firebox that is 3461 cu in. So my question. Do I need to combine these 2 calculations and have a firebox that is 6725 cu in? Should I keep the tuning plates in the round one or turn it somehow into a reverse flow? Any suggestions would be really helpful. Thanks Guys.