squeezing more hp

Start at the top of the engine and work your way down before going inside. Since it was rebuilt, I'll assume the cam is what you want in the power range you like.

Air cleaner. An open element is best, a K&N or equal filter is an upgrade as well as a extreme top for extra breathing.

Carb. I like T-Q's for the explosive secondary feel they have, but a well tuned carb is good no matter what make or style. Tune tune tune.

Intake. A hi-rise dual plane is best for the street. (To bad Edelbrock dosen't make on doable for a T-Q.)

Heads. Well preped heads and valve job goes along way. Cam and performance RPM dependent, bowl porting is a nice addition.

Headers. Coated headers or wrapped if you go for that keep heat in and force it to leave where the heat isn't, faster.

Pipe size and style. At 300 hp, 2-1/2 pipe size is a min. (IMO and other manufactures opinions). A X pipe seems to show the best output. H 2nd, dual 3rd.

Muffler. A high flowing muffler can be loud. Catch 22. I went with Hooker Aero Chambers with my mostly stock 440 B engine. (I added a viscous fan, K&N in a trap door intake from a '73 - 340, FBO ignition) There actually quite enuff to have a convo in the car without shouting.

Ignition. Top of the line new parts pay, and pay well in the long run and the right now. Gap plugs wide.

Get rid of parasidic loss. If you can do a electric fan and water pump, your freeing up power instead of turning the pulleys. That also includes A/C and P/S.

A 4 or 5 speed tranny will help in torque release. That'll feel like a great power added.