(Brian pores over the manual printout to see how we screwed up.)
After waiting a few weeks for Brian to be free, we managed to get the radiator back in Greta. We installed the new Nissens to a T, and started her up-fine. We then shut her off and began to add coolant. On the second start, I heard a "Kerrang!" and immediately saw new coolant spewing all over the engine bay. Somehow the fan managed to touch the new radiator and damage it. How I managed to not break anything is a minor miracle.
(Our friend Jimmy D stopped by with the usual gifts of snacks and ridicule.)
It looks like my local radiator shop can repair the damage-they have some epoxy process for aluminum that is supposed to work wonders. As soon as I can get the radiator out, I'll drop it off for repair.
(We also put a new accessory belt in-like it matters.)