Your best chance is to follow the Energy Maximizer (I think thats the name) diet. It's like 75% carbs and will allow you to add mass, but only really works if your BF% is around 8%.
If you're looking to change the composition of you current weight, then I highly recommend P90X. If you feel like you want to gain 10-20lbs in the near future, then this is not at all what you should be doing.
