71 intake has better flow I believe. 72 heads have funny port notch cut outs. I can attest RAIV cams work very well in a 455, but harder cold starts, lumpy idle charecteristics, and as said with auto, shift kit and higher stall converter. I think a built HO or SD trumps a 400CI usually, but stock I would bet on RAIV with both in tune. How car is set up is big as power curves, RPM ranges, gear ratio, tranny are the deal breakers. As great as HO and SD's are, both are handicapped by less than ideal factory cams in relationship to the rest of the engine potential.
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72 Bird
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