Together, Joseph and Oliver received the Aaronic and Melchizedek Priesthood and the associated keys in the Kirtland temple.
Together they wrote the first history of the Church, the eight essays that were published as letters in 1834-5. (This includes Letter VII, of course.)
Together they testified that Joseph translated the plates with the Urim and Thummim, thereby producing the Book of Mormon.
Together they testified of its divine authenticity, including the site of the Hill Cumorah of Mormon 6:6, right in western New York.
All of their faithful contemporaries and successors have reaffirmed their testimony about these topics.
They all deserve our respect and gratitude, as well as our trust.