that is a fricken' sweet monster gt. you should run atleast 1 gallon of fuel before you convert it.
questions:
-no timeframe on the slipper, but it's in the works
-a center diff is a good idea, and will handle the power fine. Mike will soon be making this diff
http://www.rc-monster.com/forum/showthread.php?t=10233 it's for an e-maxx, but it's design will easily adapt to a monster gt, I thought of that as I had an mgt when I got that center diff/motor mount
-it's a big truck, and you have plenty of room, go 6s, perfect match for an MMM and a kb45!