Header Exhaust Gaskets

[Ernest]

Looks to be time to change them out, so Im running a ZZ4 engine with cylinder heads that use a "D" exhaust port, but using 1 5/8" headers what looks to use an oval port... would it be best to try and use "D" port or go with oval port exhaust gaskets?

Having no idea what headers came already installed when i got the car, no markings anywhere, so after going by the header flange design and the layout of the header tubes, i came across "Southwest Speed" 1 5/8" long tube ceramic coated headers(#440-2258) that lQQk to be a perfect match for what i've got, if you can actually see the similarities as well.

 

[565bbchevy]

I have a set of NKB aluminum heads and bought a set of Flatout copper gaskets to match up with my Ebay stainless headers.(which look close to the ones you posted)
This was about 7 years ago but I think these are the ones I purchased, dimensions are in the 2nd picture and since they are solid copper with no raised boss you might be able to open them up more to match a slightly larger D port.

https://www.summitracing.com/parts/fog-7002c/make/chevrolet

 

[Ernest]

I have on hand the Fel-Pro #1470 gasket set, made to fit the ZZ4 engine heads, i just havent used them yet.

Its just the sealing area to the oval looking port header flange im concerned about, the ones in use now look almost shot, even though i dont hear any exhaust leaks from them, all header bolts are snug, but i do have that faint smell of gasious exhaust inside the car while driving.