All hardtops are bought and made to fit by the customer. Advice and direction with this can be given.
Don’t forget the hardtops are made with a rolled edge that wraps around the wind-shield frame.
Below is a series of images taken by Flags of how he fitted his SWB hardtop to his orange Predator. (click any image to enlarge)
Also, this is how Sam is fitting his hardtop to his Sidewinder project.
Since a GP body is slightly shorter the hardtops need to be shortened accordingly