I've made a couple of 24" smokers on trailers. Both trailers were 43" wide. Depending on your axle that should put your outside tire measurement at about 60" or so. I haven't had any issues with towing. Hope this helps.
Thanks guys. I wanted to keep this as small as possible, but it may not happen. I really only wanted to make the pit towable. Not a full trailer build. The goal was a towable pit with a small footprint that I can still roll into my cargo trailer if I need to. I think I can still make that happen, but now I will need to run the wheels perpendicular to the tank instead of parralel.