4130 is chromoly steel. GMC Denali if aluminium is going to be 6061 aluminium or perhaps 7005 for older models. If steel likely to be a high tensile steel or one of the newer high carbon steels which they still call high tensile, very unlikely to be 4130 chromoly steel which is more expensive to manufacture than aluminium these days.

I think they call 6061 aircraft grade aluminium because it's less brittle and more fatigue resistant than 7005 aluminium.