Is this the right heater core

[GMC5.3]

So today upon changing some hoses I got really luck and tore off a nipple from the old heater core, I've done a little research on people getting aluminum cores and others saying to go brass.

Has anyone got this brass one from autozone and it be a better fit than the aluminum ones
http://m.autozone.com/cooling-heating-and-climate-control/heater-core/pro-source-heater-core/chevrolet/blazer-4wd/1972/8-cylinders-5-7l-4bl-ohv/470359_0_0/?location=
Posted via Mobile Device