How hard will I throw?

I am 6'4, and 203 pounds, and 15 years old. I played baseball for regional representative team(s) and have competed on teams with strong baseball programs. The only thing is that my pitching need to be about 5 - 10 MPH faster than what it currently is. My fastball is constant between 75 - 78 MPH, and I have two good breaking pitches ( slider and splitter ). But some of the teams that I have played on have pitchers who were throwing in the 80 - 83 MPH range, these are the guys who work out 3 - 5 times a week, and are buff. Some were about 40 pounds heavier than I am. I want to know if I begin a decent workout program geared towards the development of the muscles need for pitching, If it is possible for me to gain between 5 - 10 MPH on my fast ball within the next year or so... I want to be able to throw around 83 - 85 MPH within the next two years. If there are any tips on what I can do to achieve this milestone, or any workout suggestions to gain speed on pitching it would be much appreciated. Please avoid thet rude and un necesarry comments, and I will pikc the best answer in a few days. I would really like to continue by baseball career onto university or college, but I need some help to get there. thanks