Well! That was a lot of information. Thanks! It seems there were two brackets that were welded to the chassis. One for 230s and then somewhere a simpler one was adopted for 280's. There seems to be one modification to the mounting that is an actual part number: A113 540 02 73, but that doesn't bolt to my chassis. There is one photo in the topic entry that shows a way to bolt the horn to the chassis. The photo shows, what appears to be, a weld failure very similar to mine. As I contemplate my options I will adopt this first. Thanks again, WRe!