Much as I hate to put anyone off flying helicopters, my recommendation is that at 6'5" you stand a very good chance of doing long term damage to your spine.
The Canadian Air Force did a study years ago that concluded the Jet Ranger should not be flown by anyone more than 5'10" tall.
I don't know of too many helicopters that can accomodate people who are as tall as you, either for leg length or sitting height (do you happen to know your percentile sitting height and leg length - that is where you fit in the general population as a percentage?).
Seriously, in some machines, if I wear a helmet, I scrape the overhead window, and I'm just 6'.
Sorry to throw a damper on things, but your long term health is more important than being a career helicopter pilot.
Shawn