73 340S were not very efficient either... 8.5 to 1 1.88 intake low lift cam restrictive exhaust etc build a 360 with early 340 components or specs. square shortblock. 9 or 10 to 1 unshroud valves...2.02s higher lift cam nice quench in combustion chamber free flowing intake&exhaust. true ratio rocker arms....positioned correctly over valve head.. snappy advance curve... torque on bottom.... good airflow on top stall conv. rear gear with correct tire height....its all in the combo
