Trying to stay lean while gaining size is one of the biggest reasons guys don't make great progress.
Why in the world are you doing cardio six days a week if the season's over? That's just making it that much harder to gain. You're not going to get so far out of shape that you'll lose your conditioning, even if you cut back the cardio training to just one or two days a week for a few months.
If you're looking to put on about 10 good, quality pounds, eat like this:
And train like this:
Done right, that will get you pretty far down the right track.
What are your current best lifts (squat, deadlift, flat bench, overhead press, row, and clean)?
Are you "allowed" to cut weight? I know some schools have policies against wrestlers cutting to make weight, so do you have to be within your weight class year-round?
That makes a difference in the actual short-term goals we need to set (gaining 10 pounds vs gaining 20, for example).