Here is my two bits worth. On a big rig the muffler is underneath the frame of the power unit. The pipes come up along the side of the cab, with a perforated shroud where the driver might touch it. I work for a school district in Colorado, and haven't seen any of the kids driving diesels with stacks. I think in the 80s one of the big three put out the "lil Red Express" pickup with stacks. I don't recall seeing a shroud. Perhaps they had double wall exaust like a wood stove chiminy?
