This is the 1:50000 IGM grid...

This is the 1:50000 IGM grid system that will help you choose maps in Ecuador, not only for the Ilinazas but also for other peaks. With this grid system you have enough information to order the sheets at the IGM. For example, the sheet for Chimborazo is CT-ÑIV-C1. This is column Ñ, row IV, subcolumn C and sub row 1