64 C20 Clutch Issue

[bhinson70]

My 1964 C20 has a strange issue with the clutch. I drove it and parked it in my back yard a couple of weeks ago. When I got in the other day to run an errand here's what happened.
It fired right up and I put the granny 4 speed into reverse to back out. As I let out on the clutch, the truck did not move and kept running smoothly. I tried it in a forward gear and it did the same thing. With the truck running and the clutch fully disengaged, the truck kept idling smoothly. I could even shift through all of the gears with the truck running and my foot off of the clutch with no grinding and the truck continuing to idle smoothly. My mechanic says it is possibly broken clutch linkage. I have not had a chance to check. Any ideas?