OK, so I picked up a donor 1987 Tempo, with a broken and stuck seat post. I gave removal a try, lots of Kroil (much better than PB Blaster). It "sort of" worked. A section of the seat post came out, unfortunately, the seat post sheared off, inside the seat tube, about 2 1/2 inches down the tube.
So now what? I am thinking one option is to soak what remains in Kroil for a while, and then use a long replacement seat post, and drive that chunk further down the seat tube, maybe four inches.
Its close to being far enough for a minimum insert line. Given the terrible condition of the paint, this bike may be destined to the co-op anyway (land of the rattlecan). But I thought briefly of a PC, something simple, and rebuild.
I guess cutting it out is an option as well, but its pretty far down the seat tube.
Started like this (thomson seat post, or what is left of it):
Can't really tell a thing from the after picture, but here it is: