that depends on your budget AND what your track allows for engines. if you want to go the .21 route, the MKII is the way to run with. If you want to save a little dough and go with a .28 or even a .30, those could very well be up your alley too.
The .28 in a truggy is powerful enough as it is, but i've seen a few .30's floating in a truggy. Jammin jay drove one around, the power band was similar to a light switch... on and off. Truth be told, i think that .30 in that particular video was modded.
I've got gas, and I'm PROUD of it... 1/5th scalers unite!