Are the aluminum ABS wheels on a '98 Grand Prix GTP 16x6 or 16x6.5?

1998 Pontiac Grand Prix GTP's had (16 inch) aluminum 5 spoke wheels with "ABS" written on them in the center. They have the same lug pattern as my car, I am curious as to whether those rims would fit the tires I already have or not. My tires are 16x6 and say not to mount on a 16x6.5 wheel. Help me out?