I kind of specialize in King's pre-publication works. Here's a link to the proofs I own:
The intention by publishers for distributing ARCs is to get them to people who will review them (hopefully favorably) in places where those reviews will be seen and pique interest and sales.
Or try to find a gig doing reviews for a publication that would merit getting an ARC.
there from those who have access to stories prior to the general public. I live out here on the perimeter so it's
difficult to fathom how some things happen. Are you associated w/the publishing industry, otherwise?
I've been collecting King proofs for more than a decade. It's become almost an obsession.
I'm not associated in any way with any publishers. I started by searching eBay, ABE, etc. and made contact with people who were willing to part with their copies for a price.