I love King. I love McCarthy. The thought of King writing an intro to Blood Meridian is completely inappropriate and wouldn't make sense to me at all. Again - I LOVE both authors, but no one will ever put McCarthy and King in the same classification. Ever.
People that would be more in line for an introduction to this book would be Marilynne Robinson, Margaret Atwood, Alice Munroe, Salman Rushdie, or J.M. Coetzee. Even Barbara Kingsolver is appropriate.