There is a black wire, about 12 AWG coming out of the alternator harness that is grounded to where alt mounting bracket mounts.
However, there's a bunch of black wires in your photos. Pls help us help you. A simple arrow would help.
Also, try photobucket; it has been proven to wrk well with T4R.ORG and Yotatech.
Also... why are there two wires connected to your alternator positive terminal screw? Where does
that red wire go?