Unfortunately I've played with the clutch adjustment until I had no play in the pedal, and it still does it (can't check airgap as I have a scatter shield). It looked a bit worn when I put it in when I took the side cover off. Even pushing the clutch 1/3 of the way down will allow me to shift, and has no appreciable effect on how loudly it grinds.

I plan to go through it all, not just throw different synchros in. Its a '67 18 spline, if it makes any difference.

Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street