Yesterday I repeated the barbecue trick on the two holdouts. I was able to open one of them, and as I expected, the insides were fairly worn and corroded.
Today I took one of the shock links whose plug seemed frozen in place, and gave it the acetylene torch treatment. After that the plug came off easily, and the internal parts are now soaking in oven cleaner to get rid of the greasy crud they were covered with.
The shocks and their arms and links are the last remaining greasy/filthy chassis parts. Every other moving part on this car has already been cleaned up, fixed up, and refinished. In the next month or two I can get all the shock parts completely cleaned up, and I will have a 100% crud-free car!