Setting rear axle

[wjjeeper]

I'm going to be putting drop blocks on my rear axle and adding an adjustable trac bar.
What's the best way to measure the L/R placement of the axle when I set the trac bar? From frame to back of brakes possibly?

Also what's the best way to actually adjust the bar? Set the axle and get a measurement for the bar length I presume, then fine tune from there.....?

Thanks for the help fellas