All #243 heads are LS6/LS2 they are the same bare casting with identical ports 210cc/70cc, 64.5cc combustion chamber. They both have D shaped exhaust ports. If you look at the exhaust side of the head, you will see triangles cut through at the spark plug location. This means that the head is a SPM (Semi Permanent Mold) casting. Without these cuts, you will have an inferior flowing sand cast head that is worth a 10hp loss. You can call those LS2 based on their manufacture date sometime in Sept. of 04' and on, but they are totally the same bare head. I reused my sodium filled valves on my Stage II LS6 #243 heads.

 

What about post #7? Those are clearly marked 243 heads but that exhaust port looks circular to me, if you tried to use your stock LS6 exhaust manifold gasket on those it would partially block the port. I had to buy new exhaust manifold gaskets (2005 Vette) because my D-shaped 2002 LS6 gaskets would block part of the exhaust port on my etp heads. The 2005 gaskets were perfectly circular and fit like a glove. I'm starting to get

 

They are a D shaped port, the flat portion it out of view at the bottom. Here is a pic. of a LS2 head exhaust port.
http://www.gmhightechperformance.com.../photo_08.html
Most headers come through with round inlets at the collectors. On my Kooks, I had to use a GM LS1 2 piece gasket.

 

Alright, I can see that I was probably missing the actual shape of the port because of the carbon build up around the port making it look circular. Kind of threw me for a loop because when I went to get new header gaskets the guy at the parts counter said "you need the ones off the new vettes" and sure enough they fit perfect. Why use a D-shaped gasket on our cars and a circular one on the 05-up if the head is the same? Thanks for clearing this up for me and sorry if I caused any confusion.

 

Actually they are round port. Here's a better picture.

 

it looks to me like the header/exhaust manifold had round ports and soot formed around it making it look like a round port on the head.

 

Bingo.

 

yep...you can see the soot line..

 

Yeah, try cleaning them first. The truth will reveal itself.....