'73 was one of the worst if not the worst year ever for emission controls. Dont remem all that they had but for starters I'd run ported vac directly to the dist then rework all of the dist subsystems in order; initial/total/springs/vac adv and carter AFB or edelbrock pri jets from a strip kit will interchange/fit on carter 2bbls so you can jet up (pick a strip kit w dia's close to what you have in your current '73 carb). They tended to have retarded cam/tim sets also