RCInfinity,
Powerful engines as in the likes of Rody tuned RB 5 port engines, JP 5 port engine and NovaMega's own MS tuned 5 port engine.
I actually do not have problems with stripping the front 24T on the one way in the Impulse PRO like what Pit-racer claimed.
Besides, I think a Centax clutch and a 13T / 50T gear ratio is pretty punchy enough.
As for battery packs, I don't think Serpent has one out yet for the 705. It's pretty easy to assemble. Get 5 pieces of AAA battery. The largest capacity is of 750 mAh flavour from Sanyo. You can get the ones with tabs and ones without (commercial and non-commercial ones). Line them up (4 at the bottom and the last battery exactly at the top of the 1st or the 4th battery at the bottom) and solder them in series. You need to get a battery connector by the way to connect the battery pack to your receiver. Heat shrink it, put in the 705 battery tray and you're set.