no tach wire

i have a harness was told its out of a 2004 dbc 6.0 chevy truck and there was no wire on green connector pin10
the pcm im using is out of a 2003 dbc 6.0 chevy van
was wondering if i can just add a wire to pin10 and do i need to change anything in programing? i am using a 81 camaro tach but im not for sure it works so i tried a aftermarket one and it goes to like 7k at a idle and stays there

now in VCM - engine - general - tach output - type - 12V pullup or no pullup
i change the resolution -high - to 4
and i change resolution - low - to 4