Well it may not be correct, but I have never used a torque wrench to torque down the injector line nuts. I have done about 10 injector installs and never had a problem. I was told by more than one diesel guru not to worry, the goodandtight standard is just fine.
If you must torque them down correctly you need a 19mm crowsfoot that will attach to your torque wrench. There is a correction factor when using the crowsfoot as it makes the wrench longer. No big deal you just have to factor it in. I also have no idea how in the world you would ever get a torque wrench on #6. Heck I have trouble getting a shorty end wrench on it.
JR2