if you're gonna do it, do it right. a hard top uni-body car uses the roof structure as part of the frame.

remove it and you get a floppy car.

so you'll have to add metal back in somewhere. either frame ties and other stifening members, or replacement 'vert metal and make it like the factory did.

it can be done, but it'll be a lot of metal work, much like doing a custom chopped top on an old 40s rod.