Here is a likely useful reference that I just found.  If anybody knows 
anything about it, please let me know.  I am going to peruse it over at 
the Library of Congress one of these days.

Jiménez Vizcarra, Claudio.
Indice del Archivo del Juzgado General de Bienes de Difuntos de la 
Nueva Galicia, siglos XVI y XVII / Claudio Jiménez Vizcarra.
México, D.F. : Instituto Nacional de Antropología e Historia, 1978.
61 p. ; 27 cm.