Dart's new high performance LT-1 cylinder head.  Finally, an LT-1 performance head that is affordable.  These are heavy duty castings with a 58cc combustion chamber and 200cc intake ports.   A perfect fit for 383cid and larger engines  As cast, the intakes flow 275 cfm at .600" lift, and the 1.437" dual springs have 140 lbs. of seat pressure and will handle .625" lift.   Catalog page here
Dart Pro1 200cc LT1 Heads......$1379.95