What brand of penetrating oil did you end up using, @the_riley? I've heard some work better on old rusted stuff. That acetone and transmission fluid mix noahc14 talked about seems like a tough fix for frozen springs. Did the oil loosen things up fast or did you wait a bit? I wonder if certain types cut through gunk quicker.

That "trace body diagrams" part just gave me major flashbacks to my old sketchbook.