Large frame (37 to 48 HP) adjustable side link.

[Reg]

Maybe heat it up with a propane torch to free it up? Then it should have a grease fitting to lube it after it is freed up.

Unless/until I know that none of the washers in there are some form of "plastic" I won't put heat to it.
i.e. I don't want nylon washers to become molten globs - b'sides burning paint off would lead to rusting, or re-painting.