Generation IV External Engine - aftermarket headers w/ d shaped ports??

OK, I'm a newbie here. I've acquired a LS7 and will be looking for aftermarket or custom headers. When I pulled the stock manifolds off I noticed a D shaped exhaust port. What aftermarket company sells headers with this shape? What have you guys used?

Thanks

ok, newbie from now on use the search as this has been asked several times in the past few weeks. LOL anyways i got my custom headers from american racing. they are all stainless and top notch crew. u cant go wrong with them or kooks.

I've already seen some posts regarding this same issue. Sounds like round flange will work. Next question. Can I buy aftermarket flanges that have the same hole pattern in case I want to try to make my own headers? I have a couple directions to run the tubes, not sure which one is best.

Anyone know of a header kit that's decent?

I've learned my lesson. :)

How does ordering from american racing work? I thought that if I needed custom headers I'd need to call someone to come out and take measurements...

OK, I'm a newbie here. I've acquired a LS7 and will be looking for aftermarket or custom headers. When I pulled the stock manifolds off I noticed a D shaped exhaust port. What aftermarket company sells headers with this shape? What have you guys used?

Thanks

Kooks will put d port flanges on your choice of headers for an extra $125.

I emailed american racing about their custom headers. I'll also contact kooks about their headers. Worst case, maybe they'll sell me some d-shaped flanges.

Thanks for the replies.

It wouldnt be worth the money if you can just get a good set of 1 7/8 headers. The d shaped port is to help speed up the exh. flow out of the head and as long as you have a non restrictive set of 1 7/8 you should be fine. my 13/4 are working fine for me but i would love to go to a 1 7/8, it would definetly net me some more power.

I do not understand the D shaped port thing. The exhaust ports back to 243s were/are D shaped and the header's inlet flange is larger than the port so?