Cylinder head discussion 340 with stock above deck pistons

Here’s why I ask, say you start with 275 hp out of a stock 340. Then just adding the 100 shot you’re at 375 hp running 13.1. Not even considering the headers. I’m at about 400ish HP mid 11’s. I’m an auto your stick, but there seems to be low hanging fruit without changing heads. I’m 410 Ci you’re 340, but still seems there is power not being used.
2.0 60' 13.1 at 108mph im running micky street slicks 235/60r15 if I can increase horsepower and get a better 60' that would be even better. I've always wanted to get better heads and increase some power. And lower the weight on front end too