SqueegUK- I've run both engines you suggested in my Truggy at the Silver State race a couple of weeks ago. From what you described, my suggestion is to go for the .25 with an .086 pipe because if your buddies are running big blocks, this set up will be close to theirs. In regards to runtime, the .25 will not disappoint you. This is an awesome engine with tons of power. I used a Dynamite pipe. I like them a lot. Not too pricey and perform well. Hope this helps.