ford 631

Starting my own thread instead of continuing in another. Dad's 631 seems to have a stuck clutch. Last summer i drove it around some, hitting brakes, trying to free it without success. Today while visiting i used wood to block the clutch down. There is practically no resistance when pushing...

What is the purpose of the spring, washers and cotter pin that I've circled in red? Mine are missing and wonder if I should replace them.