OP are you using stock upper control/camber arms or adjustable? i think an exact length isn't commonly posted because as GTSboy says, it's relevant to the individual setup. It's prob 2 years back since i did mine - numbers are written down somewhere in the garage but to quote numbers through a foggy haze of memory, i think i measured my traction rod at 218mm stock length bolt to bolt, and ended up at maybe 223mm?
The point was though, the 'best' length in my testing, was changing it by the same ratio as you change the camber arm to reduce camber once the vehicle is lowered (my rear camber is -1.75 deg). I would imagine Nissan spent a fair amount of time to minimize bump steer when calculating the suspension geometry so it would be no surprise that maintaining the same relative lengths on the arms would give the best results, to approximately maintain Nissan's geometry.