Here is a good summary of Vortec head info from the old Sallee Chevrolet web page:
http://www.sallee-chevrolet.com/Cyli...ads/Vortec.cfm

If you use stock rocker arms (guided type), you shouldnt have any pushrod problems.

This web page also discusses the misconception that there the two casting numbers are different in performance...like the web pags says, there is no difference.

The Vortec head has no water passage into the manifold, hence it does not need the center bolts. The eight manifold bolts are special in that the bottom into the head to keep nimrods from overtightening...a common Chevy manifold and valve cover problem. My name is Mike and I'm a nimrod too...I'm guilty of past overtightening and slathering the gaskets with goo to try to seal them.

mike in tucson