Wayne,
Thank you very much for taking the time to discover this information and sharing it with the community!
For me, this is incredibly useful.
re: horns not as loud… I read through my service manual for the 68’. In it, it describes making an adjustment to the horn, based on voltage readings across the horn, to make it louder or softer. Take a look at your service manual to see if it says something similar.
Ken
ROA#16567