Just depends what size truck and type of handling you want.
For a 1/8 scale monster truck for bashing or can be made to handle good if you wanna race the MGT is an easy conversion with an e-maxx tranny.
http://www.rc-monster.com/forum/show...&threadid=1234
If you want a slightly smaller truck with very good truggy like/race handling that can also take a beating,Mikes g-maxx chassied revos (G-Revo)are the ticket
http://www.rc-monster.com/forum/show...&threadid=1076
If you want pure race handling,convert a truggy/buggy with a center diff like the lightning stadium or the HPI hellfire which will be out by christmas.
The G-revo is the probably the best allrounder i reckon.
Just my suggestions,if you want to be creative and do something different,then more power to ya.
Of course there's always the good old e-maxx,takes a fair wedge to make a really good one though, whereas the revo front and rear ends are pretty much good to go.Maybe some ally diff cups are probably all you really need for the revo.Daf says the sliders hold up well too.(although it's a little less drool worthy than some of the maxxs here with parts from UE,FLM and so on)
Oops,i nearly forgot the savage.Serum will keep you right if you want to convert a savage.His savage is real nice,with lots of custom touches.
http://www.serum.demon.nl/NewBorn/