67_ls1

I’m having a starting issue with my 6L in my 66 Chevelle. I have been thinking the whole time that it was the neutral safety switch incorporated into the shifter but while waiting for a new one to arrive I bypassed it and the symptom is the same.
It won’t start unless I move the shifter back or forth slowly to catch park or neutral just right. The shift linkage just falls right into position on the shift arm when in park so I believe the linkage is adjusted correctly.
Has anyone ever had issues with the internal mode selector switch? My transmission has about 3000 miles since new so I can’t believe its wear.
And how difficult is it to change?
Thanks