Back to the original question, to give a straight answer, yes, it would. All PR3, PR4, and P72 B-series heads use the same exhaust manifold bolt pattern. It may poke out the bottom a few millimeters more, no big deal. The problem would be connecting the header to the rest of the exhaust, as in you will most likely have to shorten or extend a portion of the exhaust for it to mate up.