Not only are specified powers constitutional but all the means to implement those specified powers (unless expressly forbidden by or contrary to the spirit of the constitution) are constitutional as well.
The most profound discussion of constitutionality is in Hamilton’s essay on the constitutionality of the National Bank. He was not only the greatest lawyer in the nation but on the Constitutional Convention and the principle author of the Federalist papers which explain what the constitution means.
Anyone concerned with the constitution should closely study this essay.
No, not all the unspecified means. You are under the spell of Marshall and Hamilton, who had a mania for implied powers. Do you honestly think something so big as a central bank could be hiding between the lines of the Constitution, and that it just slipped the Framers’ minds? No.
Unspecified means of implementing expressed powers must pass the necessary and proper test. Marshall fixed the game for the Bank of the US by pretending “necessary” means not that it couldn’t live without it, but more along the lines of “helpful” or “convenient.” In this he had a modicum of justification, since at some point the Constitution contains the phrase “absolutely necessary.” If it was necessary to add the word “absolutely” in that passage, then “necessary” on its own can’t very mean without it whatever’s at issue will die.
Okay, but isn’t there ground between merely helpful and absolutely necessary that “necessary” falls? Is a central bank necessary enough to handle public debt for it to pass the bar of not being in the Constitution? Hell no. There’s a reason we conservatives abide the principle of “strict construction.” Because when you must construe constitutional language, and no matter how clear it is often you must, the endless temptation is to keep adding. Oh, are there implied powers? Well, what about the powers implied by the implied powers? And the powers implied by them? You see the point.
This works the other way, too. People are prone to construe away legitimate powers. But in the balance, and especially according to SCOTUS, extra unspecified powers have swamped the original plan. There’s no way I’d believe in a million years the Framers’d leave something so big as a central bank to implication. There’s no way a central bank is “necessary” to running the treasury or handling the state debt assumed by the fess (yet another extraconstitutional Hamiltonian move) .