what would cause...clutch cable?

The binding common to adjustable cables is often due to misplacement of the adjusting nuts on the fork end of the cable. This will also cause the cable to wear and fray. Both nuts should be on the back side of the fork so that the domed nut faces the fork and the other nut serves as jam or locknut to the domed nut.

I have the same setup, the only additional step was to put a sheetmetal screw through the eye in the firewall mount. You will need to drill a hole using the eye as a guide, then install the screw.

When properly installed, there is preload on the cable so that it does not come off the quadrant.

The adjustment is simple, you hold the cable so that it doesn't turn (visegrips) and tighten up on the domed nut that is riding against the clutch fork. Tighten until you have taken all the slack out of the cable and tighten another inch more.

I like to have the clutch completely disengaged and still have about 1.5” travel left before the pedal hits the floor. If I shift only when the pedal hits the floor, there are several milliseconds that the clutch disk is not being driven by the engine or transmission. In theory, this lets the disk slow down some and makes less work for the synchronizers – keep in mind that this is a theory, but it seems reasonable. This means that I have only about 1” of free play at the top before the pedal starts to disengage the clutch. Keep in mind that these figures are all approximate

Well said..