......................Accurate is correct for 1971 and later........68 -70 the drivers side was 2 inch for about the 1st 2 feet.............pass side was 2 1/4 rite off the manifold...........kim.........
Oldkimmer is dead on. With the 49-53 casting exhaust manifolds (68-70), the left head pipe up front was 2" O.D. and increased to 2.25" at the intermediate pipe. But we do make a custom head pipe that has a 2.25" flange pipe for automatic equipped applications.The right side has a 2.25" flange pipe and this is how our head pipes are manufactured as well.
71-74 is different as mentioned by oldkimmer. The right side 623 casting is a ball joint(no gasket) style connection and requires a 2" flange pipe.
