In an excellent demonstration of my manual dexterity, I managed to break the nipple off the filler neck of the GTO's radiator while removing to get the timing cover off.
So, now I've got a big-ass aluminum unit coming in next week. I took the old one down to the radiator shop and basically asked to be upsold, because I'm sick and tired of the marginal cooling performance of this car. I'll probably also reinstall the electric fans, and run the Sniper's fan control lines up to some relays in the space above the fender well with the vacuum pump for the brakes.