Sounds to me like things are just wearing out and probably time for a clutch kit. My '65 started shuddering a few months after buying it and gradually became worse along with noise from release bearing. At first I could kind of find that sweet spot to accelerate more smoothly but, after a bit, it was all shudder. Threw a clutch kit in and she was all good up 'til I installed the T5.
Your disc could be glazed. Your flywheel could need resurfacing. Oil could be getting in there. You pretty much have got to take things apart to see what's goin' on so, you may as well just install a new kit while you've got things apart. Or, drive it 'til you can't stand it anymore or 'til it breaks but, speaking from experience, it pretty well sucks when you're out and about and the clutch decides to take a crap.
-David
Kustoms-and-Sleds
