I improved the "stirring a bowl of oatmeal" shifting on my '72 by
installing a new rubber/urethane + metal "u-shaped" thing that goes
between the shift rod and the trans. (can't remember the part name).
The rubber on the old one was badly disintegrated, it was a wonder it
could shift at all.
It didn't cost much at all, around $12 I think.

Alistair