Dilbert, the 113, which was the main Army Personel Carrier, (and later versions still are), is also made out of aluminum, actually, it is a laminate, with a thin steel plate between aluminum sheets. The things will actually float.
Talk about underpowered. The originol 113's had a 318 Chrysler Engine, that old "polysherical" chambered thing of the late '50's and '60's. Later versions, (M113-A1) were Diesel.
When you look at pictures of Personel Carriers in 'Nam, you will notice that most of the time the guys were not in them, they all road on top.
As for the name, just about any old Army guy will always say "Track" when referring to a APC, as in "the damned Track is broke down again". Tanks, I guess, are always tanks.