PATRIOT TIGHT TUCK HEADERS, STEEL, METALLIC CERAMIC-COATED, SET OF 2 -- For off road use - Not legal for use on public roads and highways; 1.63 in. tube diameter, 2.5 in. 3-bolt flange collector, 0.31 in. flange thickness, 16-gauge primary tubing, standard head flange; Includes gaskets, header bolts, and collector reducers; 4-1 design; Oval head port; Manufactured from durable 16-gauge tubing; The solution to problems associated with engine swaps in modern street rods; Fits in the tightest of engine compartments and clears most stock motor mounts; Due to variations on motor mounts, Anchor mounts left with part number 270-2221 and right with part number 270-2220 or equivalent is recommended; Left mount may need to be ground by 0.25 in. to provide clearance for collector; 157 tooth flywheel use Ford Racing Mini Starter part number M-11000-B51 or equivalent 167 tooth flywheel use Ford Racing Mini Starter part number M-11000-MT164 or equivalent; Universal block hugger design; Tucks very close to engine; Fits P-type cylinder heads; Designed to fit engines with forward sump oil pans; Does not fit 55-57 Chevys, Camaros, or other modern vehicles with a crossmember below the engine's center two exhaust ports.