Hey 5150, I'm using the SA314B mounted behind the front grill where the stock horn used to be. I cut down an SABKT1 vehicle mount so that it would mount on top of the upper cross member. I'll take pictures tomorrow to show you. It's not the best setup, but I was working with what I had available.
The wiring is a little "hackey", I pulled the speaker wires and a trigger wire from the front, and have got the horn being triggered off the stock horn output. I wanted to trigger off the actual horn pad, but I wasn't in the mood to disassemble the steering column when the Toyota diagrams show what looks like a common ground for the horn pad which would have made it necessary to cut wires (AFAIK - I'm not a pro, just a geek.

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I then ran power from the interior fuse box (I think I'm going to splice into the horn relay power but right now am just jammed into the accessory fuse), and grounded just below the amp where there is a vehicle ground point. My goal was to do the minimum amount of "damage" to the vehicle.