I found most the parts of the arm in the stock pile at MITERS. The basets of the pivoting blocks were milled flat, so that they would not lock into the slots on the 80/20.
The monitor can't move freely like expensive arms that use springs to counterbalance the weight of the monitor, so it has to be adjusted by loosening the joints with a hex key. The part the monitor attaches to came from Samsung's original stand, and can tilt as well as rotate 90 degrees.
Here's the final 9,561,600 pixel monitor setup: