Hi, allthough I'm not the most knowledgable one when it comes to narrowing down paticulars on things like this I also have heads on my "350" with the same casting #'s-462624 and have been told that they are a stock chevy head that definetly is not vortec. Mine actually trace back to a "76" 350 motor and I have them on a "73" block. Am running a holley street dominator dual plane intake with the standard six bolts down each side. Unfortunatly, I have also been told that these are pretty low on the list of the "good" high performance stock heads. And as DennyW stated I was informed that they are crack-prone, also. Personnally I am looking at some DART Iron Eagle heads from S-D for about $750 complete with bolts and gaskets. They seem to run ok but I'm looking to get a little more out of mine. Good luck with them.