I finally finished reading the whole thread and there is good info on this thread.
I started my build of my 8 2.0B in Jan. 2010 and chose to do it piece by piece (way too expensive, never again).
I started out with the Matrix chassis and the Castle's conversion kit.
The chassis was great but the Castle kit uses cheap plastic for the batt trays and they break pretty easy. Now this was my first race season ever so I was more of a basher on the track and maybe for a seasoned racer the Castle kit would be fine, but for me it forced me to change setup so I could finish a race day with no worries. Oh by the way, Castle does not sell just the plastic batt trays separate and by my third kit it was definitely getting old and I have gotten pretty consistent with little to very minor crashes.
So I tried the Losi conversion and didn't like it as much as the Castle's kit that allows a batt to be on each side and the motor in the middle.
This got me to buy a Tekno conversion kit (just for the chassis) and use parts from each kit to make my own conversion.
So my conversion uses the Castle motor mount on a Tekno chassis to use TP 4s 3200mah 40c hard case on each side in parallel.
This setup is allows me to run two 40c lipos in parallel which gives me 6400mah but the C rating goes double offering me way more power throughout the entire race (20-30min mains).
The rest of my setup is MMP/1512 1.5Y (motor has 8mm shaft w/front fan, finned), 7940TH, CCBEC w/MMP internal BEC controlling the transponder and receiver.
The parts on the car are mostly from UltraRacing, a couple from KingHeadz, a complete package from LunsfordRacing for my screws, links and pins and ACER bearings.
I race on a 190'X90' track with really fast guys and by the middle of the season only hit the podium for third and swore before the season ends I'll take first and was told that I was dreaming.
Well the last race day I finally did it and beat the guy who I was always behind, my only regret is not reading this thread a lot sooner.