A high torque motor, 6.03mm tight bore, piston+piston head, and cylinder head.
It would pull it, but it was fairly sluggish. I can't wait to try it with an 11.1 lipo. I personally wouldn't run a 8.4v in it ever. If you don't feel comfortable with an 11.1 lipo, then I would recommend getting a 7.4 lipo, it's pretty much a 9.6v nicad but with a little snappier response. Check out Hobbyking, here's a good 7.4 lipo:
http://www.hobbyking.com/hobbyking/s...FT%5FPack.html
I've bought a bunch of lipos from these guys and their prices are great for good quality products.