Thanks for all the help
. Here's some more info:
Doc, yes I am trying to do a stock swap out on my 1939 Ford Panel truck. The Panel is a restomod, with a 350, Mustang II front, and GM steering column and trans. The "stock" or existing horn worked. It is mounted underneath the front fender, forward of the wheel. There are a few wires that come out of a hole under the fender, including the front hi beam, lo beam, and HORN. None of these have a relay as you discussed, but it is possible they are relayed back near the harness underneath the dash. I'll have to look. The car has power windows, so I hope they're using a relay since most of you guys say its important.
Last night, I hooked the existing HORN button to the + on the ooga, and used a spare wire I had laying around to go from the - on the ooga to a bolt on the frame. The ooga worked, but of course I didnt have the ground wire secured and the vibration from the ooga sound made the ground wire fall off. So I'll need to try it again today and look and see if there is some kind of relay. I am hoping if a relay is needed, they did this under the dask where I see a ton of wires and the fuse box.