Guys, I loaded this thread somewhere here and it disappeared!! I’ll try it here: Photo is of my 1973 Jeep CJ5 with thoroughly leaned-on, cammed Chevy 350 V8.
Air receiver in back, one horn can be blown at a time, note the 3/4" airline just under the mirror, to M5 in center.
Horns on top, L to R: PO123L4, Burnett M5 #248, Leslie S5T retuned to major 7th. K5LA in front of windshield on special mount.
Photo taken in 1985 by my bud, the Legendary JJ Young Jr. with his giant camera. 
Oh boy… you got bitten by the bug early didn’t you 
Thank goodness I didn’t get into train horns back then - I’d be far more broke by now.
What did you use for vehicle compressors back then or was it just a tank you’d fill up?
Back then we used under hood belt-driven big rig compressors, the one in the jeep was 2-cylinder water cooled. My late bud Bill used a 4-cylinder tire repair-truck compressor, where you had to open the hood, then the compressor came on and filled the tank up quickly. I liked my 2-cylinder truck compressor better, because while driving, it kept my 30 gallon ASME receiver filled to 125PSI at all times.
EDIT: Yeah, I have been fascinated in the musical sound of warning in railroads since 1st grade. My very first horn was an M5 back in 1974. I also started collecting the things that REALLY got me into these wonderful sounds, the big steam locomotive whistles.