Spray with WD40 and tap it around with a long drift and a hammer.
Does the mechanism look rusty?
no rust but it did sit for 20 years out in the elements.
I'll try tapping it, probably just gummed up.
Put the transmission in gear then try turning it.
I had the transmission in gear, just couldn't get the spider to turn.
Ok, keep putting rocking it back and forth, try a pry bar too. Make sure pin is all the way out.