1971 340 duster. Stock engine
For a streeter?
to what end?
Headers make power two ways, but power is a function of rpm. Without rpm, you won't notice much difference.
If you have an automatic with a stock stall and 3.23s, you will hit the top of the power peak only once on the way to 65mph; namely at about 5000=43mph, and with street tires they should be spinning. You won't hit shift-rpm again until about 80mph.
So I repeat, what are you trying to accomplish?
TTIs are pushing $1000, plus you probably need a new exhaust system to take advantage of them so there goes the best part of another G. For what purpose; 20hp at 5000rpm@43mph?
There are better ways to spend 2Gs to get the power down in the speed-band where you can use it on the street.
But be warned; spinning the tires does not mean yur fast or quick; so in all likelihood, you are already traction-challenged. If you are, you should probably fix that first. And if you are not traction challenged, then you should probably find out why, first. Cuz more power at 5000 is not gonna help you at stall speed. Even if you have a clutch.