new Tach on 65 dart

RedFish said
If white is for illumination, tap a orange wire. Ash tray lamp? Radio lamp? Automatic shift bezel lamp? If you dont want it to brighten and dim with those other lamps... The red should be switched hot. Tap that.

Sincerely i dont have any room for extra attachment in my fuse box I need to directly attach the white wire to the headlight switch.

but I can’t tell witch wire I should connect the white tach wire to.