I would get the Pro version as its the cheapest upfront and you don't have to resell stuff, plus it has the best parts on it. Its all prebuilt other than tires to mount. All the crt.5 kits now have the OFNA ext chassis. They use std servos
I have the above and as Arct1k said, I use 2100-2500 35mm wide packs. I've done 3S and 4S, but I think I'm going to go all 4S and a 2200 50mm medusa motor to get all the power and runtime I want. 3S works quite well, but too much power pushes the cells a bit. More cells, more power.
Doing the much more standard 45mm packs require some creative mounting on the OFNA chassis, or the RCM chassis which is wider to lay packs flat.
The truck is very tough, the diffs are 1/8th scale diffs. They are stronger than a Revos diff I can tell you. The only weak part is the servo saver, but Arct1k showed me that if you use the rear ackermann hole on the servo saver, the thing holds up.
My build thread for pics
No pics of the BB shock mod, but see Go-ride.com's thread. Its is essential. Click my sig vids if you want to see the .5 in action.