A highly visible credits page citing the original sources, maybe? Making something that is obscure to some more visible could be taken as free advertising for the older classics you’re drawing from.
If your quibbles are on the ethics, that is a question you’ll likely have to ask yourself, since my take it fairly straightforward; if you’re not breaking the law/infringing on someone’s rights, or hurting them in any meaningful way, then you aren’t doing anything wrong.