MLT
Thanks for your comments.
As stated above, that style horn mounts on a tab on the 216 manifold. If you had a 235 with a 235 manifold you would not have the mounting tab.
Here is a reference photo (Not my truck)
pic...click... I’ve converted to 12v and the 6v horn works fine.
Good luck on your Grandpa's truck. Next time he’s over snap a bunch of pics by the truck for your photo album.
