[SFfiredog]

I thougth the Shelby heads came with 2.19 in and 1.75 exh? One problem with the Shelby heads is the valve positions. Edelbrock relocated the valve slightly in relation to the cylinder. This allows for less shrouding of the valves by the clylinder walls. The biggest valves and ports in the world won't help if the mixture entering or exiting the engine is blocked or interupted by the cylinder walls. Airflow is all about the proper combination. All of the big name FE engine builders I know of are using the Edelbrock heads. Money is not a concern with some of these builders so if the Sheby head was better, they'd be using them.
my .02
--Mike