340 upgrades.

I'd find something similar to the old hemi grind 274 deg .471 lift. You'll probably want to take the heads off and get the valves done and get the springs set up. You can get the heads cut .030 to bring up the compression. One caveat: A fresh valve job with old rings can make the old rings start to smoke. If you decide not to remove heads when you change the springs ( you MUST change the springs) also change the valve seals they're cheap. Change the timing chain and gears. You gotta be careful about intakes some are really tall and won't fit under the hood. A 750 Holley would sork pretty good too. The factory carbs are next to impossible to find jets for.

don