From what I understand all Pontiac Heads made after may of 1974 used "screw in Studs" But there were some specific heads made before that date that used them, Like all 73/74 SD heads have Screw in studs.
As Jeff stated after around may of 73 supposedly they all got threaded studs. Before that any head with a 2.11 intake had screw in studs.In my opinion they should be added to any performance build. Back in the day when I was a young mechanic we would see pulled pressed in studs even on stock low performance engines. A low cost alternative you can easily do at home is to drill and pin like we did back in the day. Here is a good page with all the head info you will need. http://wallaceracing.com/head1.htm