Update:
Despite being very careful, I stripped the lower transmission cooler line fitting on the replacement radiator. I proceeded to remove the radiator and have a temper tantrum---I threw the radiator in the grass and beat it with a finishing hammer. That made me feel somewhat better.
Yesterday I picked up yet another radiator from my local dealer. I'm happy to report that I installed it this morning without much issue (the transmission and oil cooler line fittings were still somewhat difficult to start). I vacuum tested the cooling system, and it held at -15 PSI for 5+ minutes before adding approximately 3 gallons of AC Delco 50/50 premix antifreeze /coolant (part no. 10-5027) to the system. No leaks. Life is good.