I'm thinking the same, check rockauto, Also what i do alot is go online say autozone check the part #'s on a 83 then check a 73 see if there the same #'s
the only thing that i know is different between ur 83 and any other slant (pre-75) is that it is cast crank and hyd lifters. now as far as i know there wasn't anything special about the flow requirements for the hyd motors vs the solid ones.