He was also an ally of Cardijn during Vatican II.
After the Council, he backed the introduction of the See Judge Act method among the Latin American bishops at their famous CELAM meeting in Medellin, Colombia in 1968.
Fallecio en olor de sanctidad, Marcos Gregorio McGrath (Oremos Juntos)
Archbishop Marcos Gregorio McGrath (Findagrave)
Jorge Fernando Heredia Zubieta, Los Derechos Humanos en Las Conferencias Generales Del Episcopado de Medellin, Puebla y Santo Domingo, 2004.
O. Ernesto Valiente, The reception of Vatican II in Latin America