Brand new LS3 821 rectangle port LS heads from Chevrolet Performance including valves and valve springs. 

These are the best factory head that GM offer. 

Will fit LS2, L98, L77, L76, LS3, LSA

Aluminium performance head

• Fits any LS family engine with 4.00" bore or larger
• 2.165" hollow stem intake, and 1.59" solid stem exhaust valves
• .550" max valve lift (stock springs)
• As-cast L92 style 260cc intake ports
• D-shaped exhaust ports
• As-cast combustion chambers

Head 12615879 is assembled with the following components:

• 12569427 Sodium Filled Intake Valves
• 10166344 Valve Spring Retainers
• 12582719 Exhaust Valves
• 12482063 Intake Valve Stem Seals
• 12625033 Valve Springs
• 12482062 Exhaust Valve Stem Seals
• 10166345 Valve Locks