If you need more weight on the front end, you can get THESE aluminum chassis plates that mount right on where the existing plastic one goes. I'm pretty sure the bandit and Rustler chassis are the same.
You need a 6S setting up with a 2200kv motor with 1:1 gearing to make a Slash/Rustler/Bandit hit 100+. I believe the Rustler and the Bandit are better platforms because it has a more narrow chassis than the slash but these days though Id just grab the limitless. Way better platform
Get a limitless and hop it up. Way easier. I dont think you understand the full scope of what would go in to scratch building your own 200+MPH RC or the cost involved. Heck, just tricking out a limitless is going to cost some pretty big bucks.