This issue provides thorough, methodical methods to merge two of your mutants into one. Provides a half-dozen all-new beasties (and, really, many more than that, as they evolve through their various lifecycles), and 16 all-new mutations.
A more complete review here: http://afieldguidetodoomsday.blogspot.com/2013/01/radioactive-review-wisdom-from.html