First, there is a difference between a 3rd SCV and a diverter...Which one do you really want?
The 3rd SCV, or commonly called rear remote, operates independent of everything else, it can also be use to operate other things like a hydraulic top link, or angling a rear blade...it is usually lever operated and mounted on the ROPS or fender.Long hoses would run from the new valve under the tractor, up the loader mast then down the loader arms.
The diverter is hooked to the Dump/Curl circuit of the loader, and when a button is pushed the left/right motion of the joystick now angles the plow instead of the dump/curl cylinders.
One other option is a "true 3rd function" solenoid valve that will angle the plow with a rocker switch.
WR Long has both a diverter kit and a 3rd function kit if you don't want to source a the part yourself...they include everything you will need. You usually do not save much money buying all the parts yourself over the price of their kits.