['68OrangeSunshine]

On a couple of my trucks, I've had a problem with one of the arms of the Z-bar breaking off or slowly bending until breaking. Admittedly I have had the arms bent to clear headers.
But on a 50 year old vehicle metal fatigue is common, especially when in heavy use like a daily driver. I had exactly the gripe you're describing, just before my Z-bar lost an arm. Over a period of a few months I had to gradually add length to the clutch pushrod to get the throw-out bearing to disengage. It finally broke in rush hour traffic on the way to work. I had to bail from a job and get towed home. Once in my carport, I pulled the Z-bar pieces and took them to a welder buddy.
Look closely at the joins of the arms on the Z-bar at the junctions of the upper clutch rod and [lower] clutch pushrod.
"Z-Bar" is slang for the clutch thrust bellcrank, if you're new at this.