How to modify the car trunk so stylish

No the Saris Bones trunk racks are not compatible with your 1999 Pontiac Grand Prix with standard spoiler. Neither are any of Yakima Racks trunk racks. However the Thule 962XT and 961XT Speedway trunk mount bike racks work. They will fit your grand prix and spoiler very nicely. 962XT can carry 3 bikes and the 961XT can carry 2. No need for any addititional components to install these trunk racks either.