1973 340, want more power.

Gears not sure. Oil pressure fine, dual exhaust newer and good, has headers, runs great, automatic 3 speed
How do I find my gears? Can't really eh? Guy I bought it from said it had gears good for the highway and driving. Not low low gears.
I'd say some head work, the right cam, and you might want to spend some on a good quality converter, and you'll be about there. Not sure what intake and carb you have sitting on top....