help: terrain smoothing for super old minecraft world

Hey I have a super old world (created almost exactly 5 years ago actually... weird), my oldest world with my first buildings and such that i have continued to play on. however the change in terrain generation causing massive cliffs is really frustrating and plus it takes soooo long to find newly generated terrain. I used mcedit to delete all chunks except ~20x20 square of all my buildings and their immediate surroundings. is there some way to smooth the transition from old world to newly generated terrain? (problem is of this nature http://imgur.com/ZRWKy)