Kinda depends on whether you're after something that is comfortable and relatively quiet (so you can hear the stereo) and dependable or a "Bad Assed Street Machine" . . That looks and sounds like a "Bad Assed Street Machine" . . .
If you're gonna cruise it mostly and drive some distance with it, I'd recommend a set of cast iron Big Block Manifolds. They're quiet and a lot cooler in the engine compartment. I think there were several Corvette H.O. applications that're still around if you look very hard at swap meets, etc . . .
I have a blown small block in my Street Rod, so I use a set of the old 365 HP 'Vette cast iron manifolds with Jet Hot coating applied. Looks good, is a lot quieter and cooler than Tube headers.
On the other hand you can run a set of tubular "Block Huggers" and they'll give you a little better performance (Dunno exactly how much really) or a set of custom headers with long collectors with flanges, I've had all three on my Street Rod and they all have their advantages and dis advantages.
Probably the worst set of headers I've had on my Hot Rod was a set of High Dollar Stainless Steel tubes with long collectors. They were the prettiest thing I ever put on the Car until I drove it up the road once . . They turned every color you can find in a Paint sample book . . And they were noisy. You could hear every port fire, and when you warmed it or cooled it, they popped and crackled like a Hamburger Grill, and because my ride is in the weeds, every time you made contact with something under the car, you either cracked them, bent them or loosened them at the flanges . . I'm also pretty sure that they roasted at least one high buck Starter! If you could have put a pig on a spit in the engine compartment and driven 300 miles on a 90° day, you'd have a well roasted pig when you got there. They were absolutely the worst at generating heat in the engine compartment.
When I took 'em off, I gave them to a guy I didn't like . .
As for performance, if you have Air and all those other bells and whistles for cruising comfortably, then the parasitic HP loss (or gain) from your exhaust system won't be discernible.
And whatever you end up with, every guy who looks at your ride will give you advice on what you should have done, because whatever you have isn't gonna be right!