Still going
Believe it or not, my project still lives on... I have done a ton of research and will gladly share my best guesses on things. Here is what I have learned so far:
1) you have to SERIOUSLY trim the ECM... I did trim a little, check the fit, trim more, check the fit... Repeat. I now know how far back it had to be trimmed and if you want to give me a reference point I will measure.
2) I have PDF files for the curves of the profile of the ECM where you will need to place the brackets. The profiles came from ford cad models and someone who was able to provide me with cross-sections at those points. Heck, shoot me a pm and I'll mail you the pieces I had printed on a plotter and now have cut out of hardboard.
3) I have had a set of spring mounts cut on a jet and have the dxf files for those. The picture is not very explanatory. These pieces sit on the d50 axle and give a flat surface for the springs to mount to. The height is based on the ride height for my van with cc880s springs installed before I took the 2wd system off. If you want those files let me know. It may save a few hours of trial and error. I have already welded a set to my jig and the fit is nice.
4) I will be using the spherical bearings in the picture you see above instead of the stock bushings.
As you worry about moving the axle forward to match agile, you will soon find that it is a matter of necessity and not design. It's the only way to get enough spacing between the beams. I have about 50 pictures on my ipad of ttb setups. My plan has always been to share what I learn.
Final piece of advice. If time matters, just buy the kit. I love to tinker and my wife and I have had two boys since I began the project. Making children takes less effort. From what I understand maintenance costs on the van and children should run about parallel over time. For now, at my snails pace, It's a cheap hobby to just plug away at. I gave myself a five year timeline and am glad I did. No stress, just fun learning.
Oh and here's another underneath shot from a different van.
Have fun!