I'm getting ready to swap my 357ci. small block for a 509ci. big block. I will obviously need new headers. I'm looking for a 2" primary header that is coated inside and out. What brand provides the best fitment, and ceramic coating durability?

 

Premade headers are extremely limited for choices. The most common swap header is the Hooker Supercomp but they're only 1-7/8" primary with 3" collectors and are not a great fit.

Other choices are:

www.edquay.com
www.sandersonheaders.com
www.lemonsheaders.com

You can also buy kits and make a custom set that will fit exactly the way you want.

www.headersbyed.com

I just put on some aluminum Canfield heads on my engine this winter. My old Hookers were going to be small but didn't fit because of the exhaust port location on the new heads. I got a good deal on some Ed Quay headers with 2-1/4" primary and 4" collectors but they didn't like my heads any better. Final solution to get them in was a tubular k-member and a-arms plus a couple of header tubes still needed to be dimpled. The front subframe under the car where it angles in towards the tranny needed to be sectioned for the collectors.

I could have taken the easy route and just bought some elbows and built my own. Then they would have fit exactly the way I wanted but in the end, they probably would have cost the same.

Header coating is up to you. Many header manufactures will coat any header they sell if you want. You can always get them coated locally if you have a shop that does that. All coated headers are coated inside and out. They're only polished on the outside. The coating is durable. I heated my old Hookers with a torch to get the steering shaft past one tube. It could use repolishing but the coating is still on the tube. The Ed Quay headers that have the hammer work for clearence took more abuse than what I did to the Hookers. Only a small section where a weld joint is has a coating flake coming off.

Buy a set uncoated. Install them to see how well they fit. After doing any modifications to the tubes, then get them coated.

 

Of course with a first or second gen f-body, there's a lot more room to work with. You could probably use an off the shelf Hooker or Hedman header ordered right out of the catalog.