Out of 1 '86 GN & 4 '87 turbo-T (T-Types) turbo Buicks they've all been hardtops. Never a t-top in my turbo Buick family. Never has been, not 1 now, & never will be.
Cross bracing from the engine cross member to the end of the frame rails, another across, under the intercooler to make the 'triangle'. Rear seat braces, that is all I'm aware of as they were in the car when I purchased it.
Gary just doesn't want the sun damaging that beautiful mug of his