Had a HP 360 in a 74 RR with a 4-speed. Same basic cam as a 340. Was plenty fast. With the 73 Charger I'd put 1.6:1 rockers on the list. Shave the heads to get as much compression as possible. Pocket port, gasket match. Put a strip kit in that TQ. IF budget allows put more converter & lower gears.
When it takes more than a sweet mullet to prove you rule at the trailer park..
