Here is a good example of spaghetti western music with reverb and tremolo guitars:

Spindrift - Speak to the wind
https://www.youtube.com/watch?v=AEgNebSjNyA

But I think the charm of spaghetti western music is determined not only by guitar sound, but also by different samples, precussion (castanets or ratchets) noises and whistle. Good example of western music where the guitar is not main instrument:

Dezperadoz - Deadwood
https://www.youtube.com/watch?v=oaj9n5T5prY