318 question

you say nothing elaborate, but let me ask this: is the motor already out of the car and apart or is it still in and running.

mentioned above: what's your budget?

here's an article with basic bolt ons: intake, cam, carb and some headers that made almost 300 with a run of the mill reman long block

https://www.motortrend.com/how-to/m...t 5,000,hp by an intake, carb, and cam change
to get that 300 number, you're going to want compression and better breathing in the heads, so at least have those 302's massaged a little (put down the pitchforks, i said a little!) or diffent, better heads.