Ok, experts, what horns are correct for Rio Grande Geeps from GP30 thru 40-2, and SD40T-2 and SD45s? N scale model part references appreciated.
Don’t about part numbers, but I believe the Nathan K3LA was used in the GP’s. As well as on my truck, one of these days! Have a Nathan K3LA horn, with compressor!
According to the following post, it was a Nathan M3. https://groups.io/g/DRGW/message/60169?p=,,,20,0,0,0::Created,,horn,20,2,80,18959066 http://www.dieselairhorns.com/sounds/NathanM3.mp3
may wish to specify whether you are looking for "as delivered" or a particular period... many roads changes their specification from time to time so if you modeling 1980s the original equipment might well have been switched out. search horn blasters dot com for some cool videos!
I can't help specifically on D&RGW, i'm sure there are D&RGW experts on here. For general reference I use the following: http://atsf.railfan.net/airhorns/ https://soundtraxx.com/reference/locomotive-airhorn-usage/ Good Luck