I haven't seen this mentioned yet and maybe it's obvious. You really need a tight derailler to get good shifting onto that last big cog(anything over 24 tooth it seems) My 73 NR had enough slop that it would take on a funny angle when trying to get 1st gear. A new lower body bushing (810/1A) and spring cage cover (812/A) got me a lot closer to normal shifting.
Pete Geurds
Douglassville, Pa