We used to run with a guy in the early 70's who had a 534 in an F800 10 whl dump, and the semi guys were running Maxidynes, 335 Cummins, 8V71Ns etc. He had a set of cutouts on it, with the cutout pipes run up between the cab and body, and out the right side about window height. Once in a while one of the semi guys would flat-foot it and pass him on a hill, laughing or shooting him the bird- so he would open it up and pass them back, and just as he pulled alongside, wide open, open the cutouts right in their open window- nobody passed him more than once hehehe