1. The Dynatech MuscleMaxx exhaust kit (PN 31179391125, $583 from Speedway Motors) came partially assembled, and while it's designed to work with their MuscleMaxx header reducer cones, it can be adapted to work with any brand of header. The mandrel-bent system is made from stainless steel and features a thick, 0.060-inch (about 14 gauge) wall thickness. This system's tubing was 2.5-inches (perfect for our 450hp small-block). Dynatech also offers a 3-inch system.