I'm not 6'5". But I'm 6' 2 1/2" and have a 36" inseam.

I flew thousands of hours in king airs (1900, 350, 200, some 90 time), and a fair amount in a Baron (including two oceanic crossings with a second pilot up front).

Very few airplanes are comfortable after sitting in the seat for 2+ hours. Fortunately the king airs usually don't have many legs that are that long, it just doesn't fit the mission of the airplane. The Baron was the least comfortable by far, especially when sitting in the right seat due to both headroom and legroom. But I got through it.

I know several friends who were your height or taller that did a lot of king air flying as well. It can be done. But it takes some getting used to. As well as learning the exact technique to getting in the seat!

Good luck.