A bunch of us from the Juchipila Valley, including Juchipila, Moyahua, Rinconada and others have been corresponding in the Ulloa forum. You might try there to see if anyone remembers or knew of your grandfather or his family. There are several histories of Zacatecas that give good background for the area. Good luck on your search!
P.S. Please post only once as the more popular forums tend to get full.