how high from finished floor should blocking be installed?

Blocking doesn't have to be installed unless code required. If used, set at 4 ft. center line so you can screw the drywall into it. Today, most framers use metal T's installed in a saw kerf. In older balloon framing, blocking was needed for fire control.
T-profile strapping and L-profile strapping are designed to be installed by inserting one leg of the strapping into a 1/2-in.-deep kerf cut into the studs and plates, and then nailing the strapping to each stud and plate.
Read more: http://www.greenbuildingadvisor.com/community/forum/general-questions/21547/proper-installation-metal-strapping-shear-bracing#ixzz4EtKlIcE4