You're about the size I was when I started trying to gain weight... the first time. I had the same problem with metabolism, so I had to eat like a horse. I ate lots and lots of chicken, obviously. I also loved pasta, which isn't necessarily a negative since you're so active, and still have a great metabolism. Since you're really just looking for mass, and not worrying about staying trim, stock up on oatmeal, eggs, chicken, pasta, and lean red meat.