I am using a Moos Racing chassis, there is a thread about them in the "Product Reviews" section:
http://www.rc-monster.com/forum/showthread.php?t=27360
The diffs all came together perfectly believe it or not, I call them Frankenstein diffs LOL! The only part I was unsure of was the Sportwerks TiNi ring gears, but they bolted up just fine. I had to shim them a bit inside the diff bulks, but you'd need to do that even with the stock diffs.
I am waiting on some CF ackerman plates to show up, and now also need to save up for CF IGT towers. Another thing is finding the right spring rate for the Revo shocks. For Jato and Revo springs there is anywhere between like 5 lb/in all the way to 30 lb/in. I emailed Nitrohouse to see if they know what the Ultra GTP and DM-1 use, just to give me an idea of where to start. Still waiting to hear back.
I don't mind it going a bit slow, I want to take my time and do everything perfectly to how I want it. No compromises! Plus I still have quite awhile left until the snow melts and I can actually drive it.