These shift forks can wear thin on the ends that push the shift collars into gear inside the tranny. Not allowing it to shift far enough into gear.
If you can get the side cover off the tranny, you can probably replace them without removing the tranny from the car.
Old School mechanics would braze up the worn ends then throw them into used motor oil to harden them while they were still hot. Then machine them back to working width again.
1969 shifting forks, are more than likely worn after 50 years.
1st & 2nd shift fork, and 3rd & 4th shift fork.
View attachment 1715617634
