Small Block Ford big tube wide rectangular shaped port header adapter exhaust flanges. These flanges come as a pair and are designed for 2 horizontal centerline bolt pattern SBF heads, machine work included. Includes (8) countersunk holes for bolting 38 diameter flat head bolts to head and (8) 38 - 16 tapped holes to locate SBF flanges with larger port sizes for 1 - 78 or 2 diameter primaries. SBF header flanges not included, laser - cut from heavy - duty 38 thick carbon steel for superior resistance to warping from high heat, recommended header flanges are HFSBFTFHP188 or HFSBFTFHP200, or any other 38 thick Small Block Ford header flange with 2 - 34 width diagonal header bolt pattern.