Ethnologue divides Huasteca Nahuatl into three languages: Eastern, Central, and Western, as they judge that separate literature is required, but notes that there is 85% mutual intelligibility between Eastern and Western.[3]
Huasteca Nahuatl currently has several proposed orthographies, most prominent among them those of the Instituto de Docencia e Investigación Etnológica de Zacatecas (IDIEZ),[5] Mexican government publications, and the Summer Institute of Linguistics (SIL).[6]
IDIEZ
Their orthography is based on the evolution of Classical Nahuatl. It is somewhat of a deep orthography based on morphology since it aims to provide a unified system across regions.
uses ⟨ca⟩, ⟨que⟩, ⟨qui⟩, ⟨co⟩ for /k/
takes morphology into account
uses ⟨za⟩, ⟨ce⟩, ⟨ci⟩, ⟨zo⟩ for /s/
uses ⟨h⟩ for /h/
Mexican government publications
Is influenced by modern Spanish conventions and is a very surface-based orthography. It aims to provide easy literacy across regions but with a different writing system in each one.
uses ⟨k⟩ for /k/
does not take morphology into account
uses ⟨s⟩ for /s/
uses ⟨j⟩ for /h/
SIL
Somewhat based on modern Spanish conventions, mostly surface-based orthography as well but does not completely dispose of Classical Nahuatl conventions.
Kimball, Geoffrey (1990). "Noun Pluralization in Eastern Huasteca Nahuatl". International Journal of American Linguistics. 56 (2): 196–216. doi:10.1086/466150. S2CID145224238.
Rodríguez López, María Teresa, and Pablo Valderrama Rouy. 2005. "The Gulf Coast Nahua." In Sandstrom, Alan R., and Enrique Hugo García Valencia. 2005. Native peoples of the Gulf Coast of Mexico. Tucson: University of Arizona Press.