Would anyone here know how to identify this option , or better yet, have a picture of one? Got several extra delco units that are cast with H and L inside a circle, but think thease are just the standard horns.

Jim, I just got my 67 horns restored by Gary at the Hornworks. I looked at them and one has the # 231 and the other has #232 on it. I am not sure which one is the high or low. Hope this helps.

What are the correct GM numbers for the 67 horns? So far I've bought 4 off of ebay, and none work (and I doubt they are even for a 67)

The H is for the high note horn, part #9000232 an is mounted closet to front of car. The L is for low note part # 900231 and is mounted towards rear. Hope this helps.

The optional U03 (low "D") horn is a third horn and mounts on the front, flat area of the inner fender skirt just behind the driver side headlamps. Mounting bracket is "L" shaped unlike the standard horns' brackets that are more "S" shaped. The standard 'low' and 'high' horns mount to the fender lip itself. A relatively rare option with only 1,191 reported ordered.