Small update. I picked up a set of Delco Remy 4 note horns. 4 horns in total to make the train horn sound, apparently these used to be stock in the old caddies.
Here's the horns before install:
Here are all 4 installed, these are the two behind the front grill:
Driver side:
Passenger side:
Here is a short vid of what they sound like. I was already getting late by the time I had the wiring finished up so just tapped the horn a couple times:
I love the sound of them, they are definitely loud and beat the hell out of the baby stock horns!