4-speed clutch problem on '65 Barracuda

Hello All,
I have a 360 with 4-speed in my '65.
While driving locally I pushed in the clutch pedal to shift and felt a clunk or pop. At that point the pedal became more difficult to depress, and I struggled to get the car into gear and limp back home. Once home I can not shift into any gear.
It doesn't grind, but it is like it is blocked from going into any gear. Visually, everything from the pedal to the fork and throw-out bearing appear to operate, and I can see the disc moving. Maybe not moving enough?
It shifts fine when engine is off, so I believe the problem in in the clutch. I expect I have to remove the trans and likely replace clutch, but was wondering if anyone has an idea as to what would cause a clutch to act that way.
As always,Thank you in advance for your knowledge. RJG