How about just installing the T-case and driving? But based on the question, I assume it isn't running for other reasons as well.
Even parked in the garage, leaving the tranny hanging off the engine with only motor mounts will at least knock the distributor cap off, if not break it or do more damage to the dizzy. For pulling the vehicle around, I would absolutely support the back of the transmission. It really isn't much work to install the crossmember (4 bolts) and connect the transmission mount (2 or 4 bolts).