Coty's Wild Musk was my favorite musk and my signature scent when I was in my teens and 20s. I used the oil, which was powerful, both clean and dirty, with a sweet, powdery finish that lasted all day and ramped up from the warmth of skin.
You cannot make an all-natural version that smells like it. No natural musk is available other than the unethical deer musk (which probably never was used in Wild Musk anyway) and Ambrette Seed (which has top notes that smell like pickles and will disappoint you). Because of the time frame in which Wild Musk was made, it probably contained nitro musk or other chemicals which are banned or restricted now due to health and environmental reasons.
If you want to try some synthetic musks, use a mixture of several with different characteristics, like Habanolide (clean), Velvione (natural), and Ambrettolide (fruity). Then you can add vanilla and/or amber, powder notes, some white florals and/or rose, bergamot, maybe some sandalwood and/or patchouli -- take your best guess. It won't smell the same, but maybe you'll find some combination you like equally well in a different way.
IMO, the current EDT strength of Wild Musk (although pale in comparison to the original) is still the best musk. Other similar fragrances of that era that are still available are Bonnie Bell Skin Musk or Jovan Musk. They were made at the same time and competed for the same market. Neither of them is as good, but they have a same vibe. Doubtless, all are reformulated.
Keihl's was more dirty and simplistic than Wild Musk. It missed the mark for me.
Here is an ad for a place that claims to "reproduce" Wild Musk Oil:
My recommendation is to just buy a current bottle of Wild Musk and make do with that.