Offensive Guard, maybe offensive tackle. Your height and weight are perfect for tight end or defensive end, but speed is a necessity in those positions. If you aren't fast then guard would be a good fit, especially in a primarily focused running team or a pocket throwing team.
Offensive line is all about being able to move people around without getting in too close to them. You need to be able to understand blocking schemes, use your hands well, and have good footwork. Use sled dummies to build power off the line. Do short sprint exercises, and by short I mean 10 yard bursts while changing directions. Square cone drills are perfect.
Go to the gym and start squatting and power cleaning a lot. Focus on big weight at small reps to build muscle and then switch off to high rep, low weight every other week or two to build fast twitch muscle. For upper body, focus on Chest and Triceps. Common mistake is to work your biceps a lot. You dont use your biceps in football. Its all about pushing people around, not pulling people in.
Run long distances a few times a week for endurance, eat well, start drinking protein shakes twice a day, and work out a lot. Stretching is key as well. Do it before and after a work out or practice.
Last thing, be mentally prepared to be hit hard and often. Remember that the person who is not going full speed is the one more likely to be hurt. Be the hammer, not the nail.