Im 17 and i found a 1991 ford escort Gt and my step dad is a mechanic and he and his boss found the car and so he fixed up the car and wants to sell me the car for 350.00 which is a good price because he put all new everything on the car and it runs good just my dad hates fords and i want to know if this is the right choice for me.

OK, your step dad isn’t selling you that car. He’s giving it to you, with a nominal payment as an encouragement for you to care for the car and understand the value of money. 1) You’ll almost surely never get such a great price on a (probably lovingly refurbished) car again in your life, and 2) This isn’t just a gift car, it’s a bonding event with your step dad.

Be smart; take the car and thank the man for caring about you! If the car only lives another six months, it’ll be well worth it and "the right choice" for you.

ADDED:
Re-reading your Question, I’ve realized you might be worried about this car coming between you and your actual dad. Only you can make that determination. IMO, the argument that "the price was just too right" might defuse that problem.