How many differences fundamentally ?? Ok.. The most glaring difference.. ALUMINUM !! On average 25lbs lighter per head. The chambers are vastly redesigned to improve combustion and resist detonation. Valves are significantly lager and typically Stainless Steel for durability. Not to mention the larger intake runners!!.. blind accessory holes.. etc.. the list goes on and on. Multiple fundamental differences.

1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.