6'4" 152lb and 25 here, although I was 145 most of the last 10 years.
Interesting position you are in, let me focus on basketball first. How good are you? Do you think you will bulk up 10-30lbs over the next few years? Do you plan on trying to play in college? I was never aggressive enough for the ball sports so I never really tried to use my height in that sport. If you are so-so, or don't think you will be able to gain bulk, or don't plan on playing in college then running may be a better option for you.
Your running times are ok, they will get better the longer your in the sport and as you get more miles under your legs. Being 6'4" shouldn't really have an affect on whether you should be a runner or not. Sure at the top level it isn't as great for heat dissipation but it hasn't stopped other tall Olympic caliber runners.
I would guess that doing both sports would increase your risk of injury. You can certainly do both but it will probably take away from each. Your basketball career will probably be over in two-six years but you will be able to be a competitive runner for a long while. And it will probably benefit your long term running PRs if you start sooner rather than later. Just my 2c
- RS