You left out the 68 1/2 RA-II which was the fore runner of the RA-IV.
Cast intake and 1.5 rockers. Intake side (I think) did not flow like RA-IV. Jim Mino has probably the quickest PS Firebird around w/RA-II power and not RA-IV.
I am posting this just to make the controversy go on and on.
