Not sure what you mean by IIRC. I've heard the term, but it's not a head specific term AFAIK ? Casting #'s - But I have no idea what they are. Only other way is counting the SP chamber threads. I believe these heads are on the 03 - 07 4.6L's. Also the 03 5.4L.
Last edited by jbrew; 05-09-2008 at 02:27 PM.