With the 5.0 cars they use non ported GT40(p) heads and Cobra or Explorer intakes. Cubic inch is limited as well as total lift on the cams. Amazing times for stock-ish heads and intakes.
They are purpose built race cars. Not much is "stock" but it does give an idea of what the heads and intakes can support in non-ported form.
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General Stonewall Jackson has been quoted saying that when the time of war comes,
“My advice is to draw the sword and throw away the scabbard".