The Ivy King bomb was a modified version of the Mk-6D bomb, but instead of using the implosion system that the Mk-6D had it used a 92 point implosion system initially developed for the Mk-13.
The Ivy King bomb, designated as a Mk-18 bomb and named the "Super Oralloy Bomb", was a modified version of the Mk-6D bomb. Instead of using the implosion system that the Mk-6D had, it used a 92 point implosion system initially developed for the Mk-13.