Don't get confused..The gearbox is an EPS350C, and you want a D (6.6:1) gear ratio. The spur gear will come with the gear box. You will need to buy a 10 tooth D pinion (part # EPS-9D). Bishop Power Products has the Razors on now for $81.95, this is quite a bit cheaper than they have been for some time. He can fix you up with the gearbox and pinion gear also. As long as you are ordering, get the "CNC Adapter Plate" (it's on the gearbox page) it makes everything more solid and you can adjust the gear mesh. EDIT: Looks like the gearboxes he has already have the CNC plane.. you won't need to buy an extra.

I'm not familiar with the Thunder Power 1350's. Make sure to try to get the "second generation" or 10C discharge packs, they are a lot better than the old school packs. I can pull 20% more amps from a 3S 850 Mah Irate than I can a 3S 1200 Mah E-Tec. The new cells are really great.