Best Bar Risers

Couple of ways to go about this. You can get full sized bar mount risers like RoX (pictured below) which not only raises your bars but allows for a lot more adjustment front and back. They might look a bit goofy on a dirtbike but I have used them on an ADV and they’re solid. What I probably would lean towards if you don’t need an aggressive height change are just simple risers (more like shims tbh) that fit underneath your stock mounts. Enduro Engineering has a decent set. I haven’t personally used them but my buddy is 6’6 and won’t ride without them. Both the RoX and EE have size options and fit in stock clamps. 
 

RoX Risers

Enduro Engineering risers

You’re thinking about this all wrong.  I’m 6’4” myself and do a good amount of winning in the vet B classes for a guy with zero natural talent.  The last thing I would want to do is move the bars up and back toward me.  I run Pro-Taper Pastrana MX (RM low) bend.  Being tall, my arms are long, so the last thing I want to do is move the bars back toward me and up.  I want to make the bike as long as possible to spread my tall frame across the length of the bike.  The Pastrana (a fast tall guy) freestyle bend is tall, but his MX bend is low with very little sweep.  Try this.  You’ll thank me for it.  I was a tall bar bend guy back in the day until someone clued me in on the physics of my situation.

Moving bars to the forward holes will raise them a little bit. Forward holes with risers will be pretty tall. I’m with quadzbro on this one. Try to get along with the lower bars for a few hours before going to risers. I’m 6’2” and run a stock Honda bend on a YZ. I used to ride windhams but like the lower bars in air a lot better. 

I’m 6’5” I’ve always ran renthal windam bend but wanted to try something different so went with a rethal 827 bend which is lower and flatter with a 5mm taller bar mount and works well! 

X trig PHDS mounts have been the go to for me on almost every bike I've owned.