Bill you weren't dreaming!
Here is the site I found a while back. I have not ordered the repair kit myself, however via email they said their kits should work on other Delco GM horns for years listed. The "should" always makes you wonder. If you get more details or order - please let us know.
http://www.zip-products.com
I ordered & installed the deluxe horn repair kit ($46 w/shipping). One kit does both horns, they give you a high & low tone diaphragm. It took about two hours, the only tools I used were a drill & bits, a punch, a vise to squeeze the rivets (which will also make the checkerboard pattern on the rivets), an ohmmeter to check the coils & contact points, and the supplied file to clean the points. It took about two hours, and now my hooters are hooting again. :-))) I'll need to bead blast & paint them & I'll be done.
BL
