They do in fact screw into the top of the radiator. The factory Harrison radiators in our cars have a top portion, a strip in the middle, that's not part of the radiator. Pontiac used a couple short sheet metal screws to attach the cooler clips.
WARNING!!! Be VERY careful drilling a hole to start those two screws! You need a depth gauge on your drill, or if you don't have one, use a section of vacuum hose (or lots of duct tape) over the drill bit so only about 1/8" of the bit is showing. It's VERY easy to puncture the top of the radiator tank, so please be careful.
The two clips mount where the little notches are on the leading edge of the factory fan shroud.
