When I first received my JL - I ran a 17T and then a 13T brushed motor. My kit came with a pinion, and I used that with the brushed motors. With the stock battery holders, you can fit a 7-cell hump pack - but not a 7-cell stick (my Slash came with one - too long). I did have to trim the stock battery hold down a bit - just to clear the hump cell (nothing major). The car is a good buy for the money.
The only thing about the Titan motor - it's a 550 type. You might have to get creative on mounting the esc and receiver. I say run it with your current setup and have fun with it.
