Wow, some interesting stuff has been said in this thread.
My only comments are directed toward savageskaterkid who has some interesting choices to make. From what I understand, you have a broken daily driver and a Z car. Having been in the exact same position as you I would urge to to not give into the temptaion to do anything other than simple repairs to your Sentra. An engine swap or other performance mods will only divert time, money and interest from your Z car and then you'll have two project cars and no daily driver. Bite the bullet, fix the Sentra and continue to drive it as long as you can while you keep working on your Z and making it what you want. Don't worry about your father not making the best decision and buying you the car, you cannot change what happened so just make the best of it.
Just my two cents worth.