My base 1970 Truck has only one horn.
If you moved up in trim packages did you get another horn?
I have used "The Horn Works" before and was very pleased with the results.
https://www.carhornrestoration.com/
Since I used them the business has sold. I expect you will get the same great service from the new owner.
I just pulled my C10 horn apart and found no continuity at the points.
I filed them and the horn worked afterwards but sounded like a constipated duck.
I have a couple others here that I will use. I am not looking to build an all original truck.
Rick