The cheapest solution for a HB center diff is to find a Lightning being parted out on eBay. I routinely see the center diff's go for $18-20, then you just need the $5 Kyosho spur from Mike.
thanks guys!
jw, i dont even really want the cd, just to keep the transmission small, is there some kind of spool? i rember like a ofna denominator or something, is that any cheaper?