what yoke do i need...

As long as the 904 is the same length as a 727, you just need a 727 yoke that fits the u-joints your shaft uses. Likely the small ones. See the link for sizes and names associated with them.

http://board.moparts.org/ubbthreads/ubbthreads.php/ubb/showflat/Number/5722637/site_id/1