So I started to take apart my upper steering column to replace the turn signal switch, and when I got the horn off (two screws in the back), I had a plug for a blue wire and a tab to plug in a female spade connector with both a yellow/blue and a black wire connected together. I also have two other black wires that connect together to a spring loaded terminal-the problem is when I pulled the horn piece out, the spring terminal was not connected to anything and I can't figure out where it will go when I put it all back together. My truck has speed control so there are two additional switches on the horn panel. The wiring diagram I found online shows these two black wires going to ground but I don't know where to do this. Thanks!

 

I'm not sure where they hook up, but your steering shaft should be grounded. That's how your horn works it's a ground tripped relay.

 

What year truck?
Horn wiring for 73-77 is different from 78-79.

 

Its a 76'. I have the new turn signal switch in but am also having trouble now getting the old (cut) wires to release from the plug-can't seem to find the barb to release them.

 

The horn bar has two black wires, one with a female spade connector, this one connects to the blue/yellow trace wire. The other one has a "funky" looking terminal. This is the ground, it plugs into one of the threaded holes that you use to pull the steering wheel.
As for the wire harness locks. Look into the end of the plastic shell, each wire terminal has a little plastic tab that you have to pry away from the terminal. Do this and the wire will pull out of the shell.
GRRRRR! I'm trying to post some pictures but keep getting a 503 error. As soon as I get that straightened out, I'll post them.

 

Got it-everything works! Thanks!

 

Good, I'm still getting a 503 error.

 

A little late to the party, but here are the pictures I was trying to post.

 

Be aware that the T/S switch used with speed control is different...than without. This switch is obsolete, only a few are available NOS

D5TZ-13341-B .. T/S Switch-Use with Speed Control: 1975/77 F100/350 & Econoline.