This one is aluminum....
https://www.force10brakes.com/home/1962-74-Mopar-Bendix-Style-ALUMINUM-Master-Cylinder-1-1-32-bore-for-disc-drum-and-disc-disc-applications-p235514315
It is a factory appearing 4 bolt mount aluminum unit with a 1 1/32" bore. It weighs a third of cast iron and looks great. I've never bought from this company so I'm unsure about them.