whipnet,
If your doing a conversion on a IGT 2, I'd get with wildbillmassey at IGTHobbies. I've done mine with the Kyosho kit, the Kyosho center diff, the CC/Neu 1518 1800kv on 4S (practice) and 6S and I love it some much more than when I originally had it with the 2sp.
Also, last week I slammed the wall really hard and actually broke the output post on the front diff case. Long story short, I did some experimenting with the HPI aluminum diff case (for better strength), the HPI output cups, the stock kyosho diff gears, and the stock kyosho ring gear. Believe it or not, it all fits perfectly !
So now I'm gonna do the same for the rear diff unless someone knows of a Kyosho aluminum diff setup.