If your 40 yd time is 4.8 or better, on defense outside LB or Strong safety. On offense tight end.
If this is a high school player who wants to go to the next level: strong safety is your best bet. Forget LB you are unlikely to get taller. But the 4.8 40 (or better) is a must. If you can make 225 without a loss in speed or mobility, that would be your best plan. Don't limit yourself to defense. If what you say is accurate and you like to hit, think how many Division I coaches would like a 5'9" 230 lbs fullback that likes contact. At fullback 5'9" works better and 4.8 is fine. All the guys who tell you that they run a 4.3 electronic timed, on grass in cleats, 40; are lying. That is Deion Sanders speed and there ain't many of those around.
Cheerleader.
Defensive tackle
Bench Warmer
RunningBack
fullback?
left out or right corner
If your fast: cornerback or wide receiver
Anyone you choose! - Most coaches would have you on the line
Punter or placekicker. No speed required.
In 7th grade you would probably be an offensive or defensive lineman.
cornerback or safety
they weigh about 180-220 pounds they cant run if they are fat