74 C10 with 87 steering column

[epfatboy]

I have a '87 tilt steering column (floor/manual shift) in my '74 C10, bought the column from Steering column pro's. Put a Grant steering wheel on it, all is fine except the horn blows when I turn the steering wheel or move the steering wheel up/down. It also blows when I hit the horn button.

Not super familiar with steering columns but my guess is it's grounding out somewhere. There was a little plastic cap that came with the wheel and I lost it (actually in the barn somewhere), pretty sure it was suppose to sit between the base steering wheel column mount and the grant steering wheel mounts.

Is that the problem? If so what is the name of that part, if not any suggestions beside un-plug the horn?