Magicland - FWIW I bought this Santa Fe Alco PA powered A unit in1997 and then the matching B unit (6-18965) in 1998 and the factory installed RailSounds are excellent - LOUD and very realistic. In addition, it should be noted that the B unit also has a 'multi-chime' horn and, when running the A and B units together (with the same ID number), the resulting 4 or 5-chime horn sounds great in my opinion. In fact, although I own several Legacy diesels, I'd have to say the sound of the combined horns of the PAs is still one of my favourite engines! IMO you'd have no regrets if you picked up the B unit.
Unfortunately, that won't help, as it's for a project, and won't be remaining an Alco. Just need the electronics and running gear (though the base will need stretched 3").