In reference to whatever is the best crank length for you on a road bike, its fairly standard for cyclists to use a 2.5-5mm shorter crank on a track bike and a 2.5-5mm longer crank on a mountain bike. So if your "fit" is 170mm cranks, I'd go with 170s on a road bike, 165s on a track bike, and maybe 172.5s on a mountain bike.
For my height, I use 175s on a road bike, but I use 167.5mm and 170mm cranks on a fixed gear. You'll benefit from shorter cranks on fixed gear bikes because a shorter crank gives you a wider range of cadence and is more comfortable to spin at high cadence.