I don't have a definite answer, but from an economics perspective, it'* cheaper for GM to make one unibody and cut a sunroof hole in it, than it is to develop, manufacture, and test two different unibodies.
Originally Posted by sseidriver97
id just go to a Jy cut the roof off a car that has it stock and wire it then weld it on hehe
As long as a roof transplant doesn't compromise the structural integrity of the unibody, it'* theoretically doable. Easier than stealing the Bonneville blueprints from GM and cutting a hole yourself.