Edit: This post is for minecraft 1.1. MCedi tr1000 is what you need for minecraft 1.2. This 1.1 world generator mod is still useful as it generates epic landscapes that can be brought into minecraft 1.2. Check my newer post on how to bring your old 256-height levels into anvil format for 1.2.
I have recently become obsessed with the dessert biomes of minecraft. One of the things I’ve always wanted to do since I started minecraft, was to make a large sandstone temple. My heart sank every time I wish I could build something taller than 64 blocks high above the ground. Even after I found a height mod, I realized that the 256 height (bedrock to sky-limit) levels were not compatible with the standard editors MCedit and Word Edit. While it is fun to place every single block of large structures, editors help me get the project done faster so I can complete more of them and fix errors that would take days to correct without them. Fortunately, there is a version of MCedit which allows for editing large worlds.
Solving the height problem:
fishtaco567 released a height altering mod. You can download both client and server mod files from this link: http://www.minecraftforum.net/topic/544429-110100fishtacos-mods-better-caves-fps-height-mod/#height
Make sure you mod the server jar file and don’t try to modify the server exe file. Instructions on setting up jar servers are found on Notch’s minecraft.net site: http://www.minecraft.net/download
MCedit for higher than 128 height-limit levels:
Just click on the testing folder and download the file that goes with your operating system
Another way to get here is from the official forum page: http://www.minecraftforum.net/topic/13807-mcedit-minecraft-world-editor-compatible-with-mc-beta-18/
you’ll need to scroll down to quick links and click the old versions link.
You only have to design 1/8th of most symmetrical structures. With MCedit, you can clone your design and replicate it mirrored and rotated to make up the rest of your design.