Early to mid-1970's, behind 472 and 500 cubic inch engines. They have 2 1/2" inlet and outlet pipes. They're fairly long, but the flow rate is great, espsecially on smaller-displacement engines. I set up my son's Dodge pickup with a 318/Torqueflite running gear that way, dual pipes and mufflers with the 2 1/2" tailpipes and 3" bologna-sliced tips. It was quiet, but fast. I used the Comp Cams 260 High Energy cam in that one with a Carter AFB.
Jerry



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