I think the nearest stop to Tucumcari is Amarillo. By getting off at Sante Fe and returning by way of Amarillo you should be able to get right where you're going.
10 seconds sound clip from the For a Few Dollars More movie soundboard.
You can hear this line at 00:05:06.962 in the Blu-ray version of the movie.
Quote context
[...]
- Tickets. Tickets? Thank you. Tickets?
- We should pass there in about three or four minutes.
- Thanks.
- Excuse me, but you've made a mistake, Reverend.
- I couldn't help hearing you're going to Tucumcari.
- I peddle goods around here, and I better tell you you're on the wrong train.
- You see, the train doesn't stop at Tucumcari.
- This train'll stop at Tucumcari.
- Why'd you stop? Something gone wrong?
- Somebody pulled the emergency cord.
[...]