I think some of those black & whites had licensed characters (like, PLANET OF THE APES, Doc and Fu Manchu in the Shang-Chi stories), so Marvel is not likely to want to reprint them. Any profit would cut into by royalty fees.
SAVAGE SWORD OF CONAN and the Solomon Kane stories are available in bookstores. I'm surprised that the other black & whites like DRACULA LIVES! aren't already available. But I haven't been to a comic store in ages.