http://modernmoparforum.com/topic/5961-finally-available-aftermarket-cylinder-heads/
Mad dart here is a link and who to buy them from. Flo numbers are also in link. Im in there asking questions so you wont feel out of place. Lol
Like I was saying the cores for 6.1 heads is well over a thousand bucks. And I know they still buy them regulalrly due to they dont make them anymore. If sold and used towards the new heads one would be light years ahead. Better castings, better material, better deck thickness, ss valves and double springs and strengthened rocker stands. The flow is ten fold a ported stock cadting even of eagle castings.
The guy who designed these also designed the original faftory casting. He knows what needs imporved for power over emissions. His user id on that site is cjt as is on yellowbullet, turbobullet etc...