383 needs more power

About all you can do is change the cam to something with more lift, thats a pretty small cam anyway. and either port the heads you have or buy a decent set of aftermarket aluminum. Does this motor have headers on it now? What is your main use of this car?

I took a 383 machined in a 440 crank = 426 now. Makes 525 hp and 552 tq. Nice street manners, drives well no complaints.