rear disc from grand cherokee on a 8 3/4

Doesn't the later model JGC have a drum style e-brakes, 97-99? Why not just use the whole assembly, or is there some sort of interference? This would give you e-brakes and rear disc's, best of both worlds. Now are the calipers from the earlier models using a cable to clamp the disc for an e-brake?, if so why not have one made to fit the caliper and the factory stuff from your cars? I'm asking all these questions cause I'm gonna do the same thing, just looking for the best options.