I have a 1969 cougar convertible gt 351 performance pack. Not an xr7. The car has a factory tach. Although appears past owner changed some wiring on car for car to have a tach my question is the car has issues with wires there is a solid red wire out the back of the fuse box an I haven’t located the other wire?? If anybody can help please let me no. Thanks.
Once previous owners change wiring, the chances of any of us being able to help you is minimal. Your best bet is to get your wiring refurbished and set back to stock configuration so you’ll know what you have. See this thread for example: