I've been adjusting push buttons a long time. Things I've learned; Unless the pan is off, adjustment is a guess. Make sure the valve body attachment is the proper style.(see pic). The 64 floor shift/65 is different. The rooster comb must return to neutral (dead center) from either end of the selector ( ie R to N, Ist to N) while pulling the park lever. The plastic style plunger neutral safety switch is longer than the steel plunger style, When the plastic switch is installed there can be interference between the rooster comb where it triggers the switch and the threaded body of the switch itself. Make sure it is a 5 position roster, not 6. You can see the rooster comb position in relationship to the detent ball with a mirror in the car with the pan off. Unless the rooster comb has been bent where it engages the manual valve proper cable adjustment will center the manual valve. If you split the valve body you can see the manual valve position. Basically it should be centered on the China wall dividing the passage ways in every gear selection location.
Doug