Looking to do my first conversion (looking at a Truggy)

[Happywing]

Welcome!
You're on the right track. The ERevo is nice (I have one) but it's nowhere near as durable as most 1/8 truggies. It won't handle nearly as well either.
First, you have to pick your truggy. Truggy rollers can be had for a good price these days.
There are kits for the 8ight-T and MBX5T at this site:
http://www.rcproductdesigns.com/
These kits come with all the hardware you need and instructions for assembly. They use the existing holes in the chassis, so no drilling.
The popular choice for ESC/motor on 4s is probably this one:
http://www3.towerhobbies.com/cgi-bin...?&I=LXVHA5&P=7
Using the batteries that you have will be risky. 25c rating is nice, but they don't have the capacity to handle the motor draw. You would be better off getting a nice 4s pack in the 5000mah range and a 20C minimum rating. Prices for those are coming down.
Here's a shot of my MBX5T with the new RC Product Designs integrated battery tray:

[Ryu James]

if you are going to build a brushless truggy you cannot beat the Tekno RC kits. they are the only conversion kits that keep the mechanical brake. this has much better stopping power than using the motor for brakes and keeps your motor cooler and less wear on your motor. i have the losi 8t right now. LOVE IT!!! and will be building a custom RC8T this week. here are some links worth checking. one is to Tekno RC page of kits and the other is to the thread of my Losi 8T build so you can see how clean the TEkno kits are. tekno has a kit for the 8t, mbx5t, x2 crt, and the rc8t coming out in a couple of months. btw, truggies are the way to go. since i got my losi 8t none of my other rides get used.

http://www.impaktrc.com/index.php?cPath=238

http://www.rc-monster.com/forum/show...t=15876&page=2