Well, I guess there are at least two choices to mount these on a 1st Gen:
1.) If you have driving light brackets you can mount the horn(s) below the driving lights with the relay hidden behind the side reflector cover. This is how Scott (tooldood) mounted his.
2.) The other possibility is to mount the horn in front of the oil filter under the front spoiler by attaching it with a hose clamp to the frame tube underneath the coolant bleed valve. I think Pegstr came up with this mounting position. I mounted mine the same way, the only problem was that the hose clamp came apart after a few thousand miles, don't know if it was just a faulty (cheap) clamp or if the sharp edge of the mount produced too much strain. I am using a rubber lined band clamp right now, with a bolt going through the original mount on the horn.
According to some reports, you have to use the original oil filter housing, the mounting point will interfere with the Rivco adapter.
Sorry, no pictures of these installation handy right now, have to look around if I find any.
Klaus