Chance, the problem you mention is a SBC thing that happens due to bore distortion resulting from the change from bolts to studs. In a SBC, Smokey Yunick found that even torquing the oil pump stud measurably distorts the bores.
On a 351C, such problems do not often surface- and the possibility goes to zero if you use a torque plate to hone the cylinders. Remember- steel torque plates for iron heads and aluminum torque plates for alloy heads.
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