Mark - Just went thru the very same thing. If you will see  Pages 30.8
or 30.2 of your Bentley, You will see the Pedal and Cylinder (clutch
master) mechanism. The pins in the clevis and the pedal wear away and
almost all of the movement is lost.

In my case it was so bad the hole in the clutch pedal had worn
completely thru the side. It was a real PITA but the pedal had to be
removed and replaced. This would have been easier, had there been a
pedal available. Finally I had it welded (built up) ground flat and
redrilled, new clevis and pins and like new again.  I must warn you
about forcing the shift - the synchro between 3rd and 4th is very
vulnerable to abuse and is the primary cause of most tranny failures. I
hope this helps - It really isn't that big of a job - just tedious -
Lousy position to work- back ache etc. :-)  Keep me posted if you need
any more directions.  Bud Yandell

http://community.webtv.net/rosebud99/doc