Ofna Ultra Conversion Need Help with details

[sbarnesvta]

Hey guys im new to the forum this is my first post just wanted to say hi, i have been looking for a while and definitely like what i see. Anyways off to my latest project I am from a RC Crawling background, so speed is new to me.

I bought a used Ofna Ultra LX with the intent of converting it to electric

Before i order all my parts i wanted to get some input from you guys

So far i have planned
1- Ofna Ultra Electric Motor Mount
1- Mamba Monster ESC and 2200Kv motor combo

Gears i need some help with,
I have the stock metal gear, but i see they sell a nylon replacement. Is this necessary? if so why?
Next is the pinion gear? i am looking for a good all around buggy set up with something not bias towards torque or top end, something in the middle would be ideal.

Last thing is batteries.
I have a lipo setup for my crawler, and i was planning on using 2 3s lipo's in series. I would like something in the 5000mah or higher range. any suggestions?

thanks in advance
Steven