Exactly what class, division, sanctioning body will you be racing this Focus in?
If you want to go "racing" there are rules, very strict ones, about what can and cannot be done. When you ignore the rules before drawing up plans, you build a car that can't be used where it would be competitive, and gets thrown in an open or unlimited division.
1.) Decide exactly what type of racing you want to do
2.) See what the winners in that class are using to win
3.) Add up the build cost for a car in that class, then see that you can buy a completed race car for 1/4 the price.
4.) Decide if you would rather spend the time and money building a car, or use that time and money to go racing.
I am guessing none of this applies to you. It sounds like you want to build a "race car" to play around with, but not actually race. That's what we used to call "hot rodding", making a fun fast car to play with but not be a competitive race car within any actual racing division. That works OK with drag racing, but not very well elsewhere.