kirban 2 cents worth does not appear your caps can be saved. the design by GM was you bolt your wheel on to your car then "pop" the cap on basically the side of the factory lug nuts secures the center cap in place. the lug nuts do not tighten up and secure the center cap. it is the sides of the lug nuts that hold the center cap in place.
one answer has been give second answer is purchase a set of the GNX style 16 by 8 wheels which are lighter and has a different center cap format.
Just some suggestions.....
unfortunately profanity doesn't bring any answers the method is dumb the way GM did it....not to mention you got 30lb boat anchors on each corner....
denniskirban@yahoo.com