Sadly, none
I am 6' 6" and I have done the showroom floor tryout of all the Japanese bikes. I do not have a convenient dealer for KTMs or exotics, but I am not convinced that there is a whole lot of difference from brand to brand in ergonomics - at least not enough to make a difference for someone our size.
There are ways to get an extra quarter inch at the pegs, an extra couple inches of seat height, a few mm of additional bar offset, and maybe an inch or two of additional bar height. Unfortunately, that is not nearly enough.
FWIW, I think the KLX450 feels the roomiest on the showroom floor. But there is no bike that will fit you (or me) the way they all fit a guy who is 5' 8" tall.