You might consider using GL1 140W in the transmission.
That's what we use in all our old tractors down here in NE Texas.
Use a lot of your favorite penetrate on the clutch lever pin.
You might consider using a large C-clamp to apply pressure and gently/softly "tap" on the side.
That pivot point is cast iron and could/might break if you "beat" on it; ask me how I know.
Hope this helps and good luck with your 39B.