Be careful when trying to free up a hood that has not been opened or closed in a few decades. When "working" the panels back and forth, after applying some penetrating oil of course, make sure the panels are rotating on the hinge pin and the metal is not bending. The metal will break if it is flexing, then you will have nothing for the hinge pin to pass thru, connecting the top and side panel together. It can be fixed, but it will not be easy.
See the jagged break shown in the picture. On this panel two of the three loops for the hinge pin are broken.
Looks like that one should have sat in a molasses tub for a week then a liberal application of heat and penetrating oil. Penetrating oil alone would not be a good solution. YMMV
On one rusted hood I freed up I had to heat each loop dull red with the oxy acetylene torch until it was possible to make it start moving.
Rust penetrants are good, but in many cases heat is necessary. In a proper combination almost anything can be loosened up
Soaking would be good. Running penetrant down the rod takes quite a while to find it's way in. Putting the rod in a drill was suggested the other day to me and might work well.
I just bought Stainless rods for my project.
Soak with we-40 for a while then use low heat.
DONT heat excessively. Use just enough heat to discolor the rust.
Work the hood joints carefully!
If you use heat do it carefully and it works most every time.