new heads, will my old headers work?

ok, I'm building my motor this summer and I'm looking at getting the Holley Systemax II top end kit.
Will my old headers work? Right now I've just got the stock E7s.

Has anybody run this setup? How do you like it?
I'll either be using it with a 306 or 331. If I can afford it, I'll go for the stroker, but I'm not sure. I'm looking for around 350 horses.

They're aftermarket long tubes, no name brand.

Yeah, the little I've heard about the kit has been good...those numbers from your dad's car are getting me even more excited

Any idea on what a mild port job would run me$$? I was thinking about port matching them at home with a dremel...