Another quick report back:
Scraped rust out of radiator cap neck. Lovely.
Drained coolant. Still green, but swampy green instead of fluorescent green. Flushed with water. Added EvapoRust product. Topped up with water. Ran for two hours no load at low-mid RPM. Will run again twice a day for the next few days like this, as recommended on the product label.
After running, drained oil. It looks about as you'd imagine an oil new in 2002 would look. Extra black with lovely metallic sheen, almost like one of those fancy hot rod paints which changes reflective qualities based on the angle you're looking at it.
I'm going to run Rotella with some Lucas oil stabilizer in it unless anyone has other thoughts on the topic they'd like to share.