Jerry, if the I.D. is smaller wouldn't it slightly restrict the flow. Ed
That can actually help low end and midrange torque by increasing the velocity of the intake fuel and air gas column as it approaches the valve. If an engineer was deliberately trying to restrict high speed performance, he probably couldn't have done better than the Mickey Mouse port shape of a stovebolt cylinder head.
I don't think there's any real difference in 216 and 235 EXHAUST
manifolds except the angle of the outlet.