Re: American AutoWire
The Classic Update kit does use a horn relay that is mounted inside the car. When you look at the wiring diagrams with the kit, you'll see that AAW manages power distribution differently than GM did, so there is no need for the buss bar that was at the bottom of the OE horn relay.
I assume if you were really fussy about having exact OE appearing wiring, you'd have chosen the AAW Factory Fit harnesses. I just clipped the Update's horn relay onto the dash structure where my hazard flasher used to fit (now on the Update's fuse block), and got on with my life.
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!