I'm 5'10 with a 70 inch reach, I am fighting a guy thats 6'2 with an 84 inch reach...

[GeneralZod]

Chop down the oak tree.

[raf727]

Here is the best advice, go to the gym and train.

Asking for vague help on an internet forum where most of the people have likely never fought, or even sparred isn't going to prepare you for a fight. You have a coach, I hope, and you have other kids in the gym. Those are your best assets, utilize them. Find taller guys with reach to spar, and *gasp* develop a game plan and practice it on them.

Otherwise your going to just get a bunch of generic "get on the inside and give em hell rock!" type of advice. Go train.

Good luck.