I basically just turned my dremel into a lathe...I fixed the two identical halves into the dremel and shaved away room for the bearings to slide inward. Then, I had to modify the t-nut, spring, and one diff half slightly to accomodate the short diff screw. I also cut the diff halves to make them shorter, and used a file to shave slots for the outer rings.
I put a couple of runs on it, and it worked well.