Transform the end

you should try to get voxel sniper. it allows you to use different brushes to make different materials. so you can change all endstone into stone then set a depth of 3 or 4 for dirt. after that you can build what you wish in your new overworld!
here is a link to the voxel sniper website:
http://www.voxelwiki.com/minecraft/VoxelSniper

The end is it's own demension, it has it's own world generation, and the only way to change that would to make a mod, or build an overworld like world by hand.