216 manifold will have 1-7/16" (1.437) ports, 235/261 manifold will have 1-17/32" (1.531) ports. Same spacing port to port. 216 manifold will take the small base carbs, 235 will take the big bases. 2 of the bolts on the 4 bolt pattern where they bolt to the exhaust manifold (if not using headers) are different spacing. My favorite is to use the 216 manifold for the small base carbs and bore the ports to take the 235 alignment rings.
