They can shim-sham with the bore, stroke and rod length a little as long as they don't go over the max ci. Only dish or flat top pistons allowed so with an offset ground crank and milling of the heads the compression can vary. Nothing factory stock about the rotating assemblies.
Whatever they do....... F/S 5.0's with un-ported cobra intakes/GT40 heads run high tens.
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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".