What are you looking to do, swap rear ends and keep the drums on the 90 rear after installing it in the 94, or change all the drum brakes and stuff to the disc of the 94, and basically just use the rear end housing from the 90? Either way, the housings are the same and will bolt in place, but you will probably have to use some adapetrs for the brake lines and you would have problems with the ebrake cables if you keep the drums.