Similar design to truck manifolds but have extra material where needed to improve flow and increase strength, These manifolds fit most '54-'64 Y-block engines including 239, 272, 292 and 312 engines, Gaskets are included for a leak free installation, Exhaust ports are 1 3/8" x 1 3/8" but can be ported to 1 1/2", 2 bolt outlet flange for 2" pipe is included to connect the exhaust system.