In 2001 Dulcich dynoed a stock 340 at Westech.
With an Edelbrock 800 carb it made around 315hp. With headers it made like 330hp.

Shortly after the 2003 Engine Masters competition it was discovered why the results from the Westech dyno always seemed so "good". The barometer was way off which caused the computer to spit out corrected numbers that were 5% high(if you do a search you can find info about this).
So, take 5% off the 315hp exhaust manifold test and you're at 299hp, 5% off the 330hp header test and you're at 313hp.
And those are with the 800cfm carb, so you'd be down even farther with a correct 340AVS on the motor.
I seriously doubt there is going to be 50+hp found by "tuning".