On this episode of Dirt Every Day, Fred and Dave build a post apocalyptic 4x4 muscle car - the Mad-Maxxis Off-RoadRunner. Starting with a forgotten 1973 Plymouth Road Runner, they plan to power this one of a kind car by stuffing the next generation Cummins 5.0L V8 turbo diesel crate engine under the rusty hood. Make no mistake, this is not your standard TRAR build. This Off-Road Runner will have an Allison Transmission and a beefy transfer case to send that sweet Cummins power to all four Maxxis RAZR MT tires.