[Patrick L.]

First. How much pedal free-play is there ? Should be 1-1.5". Adjust to get that.

second. While checking/adjusting free-play check the the throw-out arm isn't cracked thru the pin.

third. Remove the transmitter top. Check the end of the shift lever, the ball should be round, but, it won't be. They tend to wear square over the decades requiring care when shifting. While in there check the shift forks for excess wear and alignment.

fourth. It sounds like you know how to drive the vehicle. It can't be driven like a modern car. Take your time between shifts. Upshifts shouldn't require a double clutch, but, its a slow easy shift.

It sounds as though the problem may be with the transmitter. It sounds like the clutch is OK. Don't try to adjust the pressure plate fingers yet. It can be done while everything is still in the car, but, I don't think thats the problem. When checking thru the inspection hole, the release/ throwout bearing shouldn't be very far from the pressure plate fingers if the pedal free-play is adjusted correctly.