I wasn't sure if this belonged in the hardcore or non-hardcore jeep section so I erred on the side of caution.
Anyways I have started a project to model the components of a jeep yj (starting with stock components) in a 3d modeler (autodesk inventor - the educational version) and then working my way towards non-stock components.
One of my main goals for this project is to build adapters and mounts that will allow the 4bt to be mounted into my yj.

I am doing this for at least 2 good reasons. Once done, all the parts I used (and manufactured) will be manufacturable to aid in the installation. It should also reduce downtime of the vehicle this operation is performed on significantly.

I have 2 yj's I can take direct measurements off of. I am currently working on the axle hardware. I am considering making plaster molds of the axles to get better drawings (although who really cares about exact dimensional accuracy of an axle that gets completely replaced?)

Here is a picture of the current progress.
http://pano.doorsphotography.com/jeep/YJ1.jpg

how did you get the shape of the center section right on the housing.

The center section for the axle may not be 100% accurate. I eventually will correct it to be accurate. To do that, I want to make a plaster mold of the housing and measure the negatives. Also, I will construct a 3d laser scanner that will help verify my model.