I'd read on Ron Kwas's website that the Amazon was originally designed so that a pull back on the turn signal stalk would flash the high beams (as on most modern cars), but that the feature was disabled for the American market during the 60's due to Department of Transportation regulations.
With wiring already in place, the addition of a three-terminal relay is all that's needed to reactivate this feature. Three wires (red, black, and grey) are wrapped into the wiring harness together near the reverse light relay.
I couldn't find a three-terminal relay, so I picked up a standard 30 amp, 12 volt, SPST relay from Radio Shack. The Radio Shack relay has four terminals (coil power, coil ground, and two poles of a normally open connection). I made a "y" harness and split 12V from the black wire to supply power to both the relay coil and the headlight. The grey wire is the "control" wire (grounds when the turn signal stalk is pulled back) and connects to the coil ground terminal. Red connects between the headlights and the other pole of the relay.
I mounted the new relay next to the reverse light relay using an existing screw. A pull back on the turn signal now activates the high beams momentarily, while the foot dipper next to the clutch still switches between high and low.
As Ron Kwas cautions, this setup isn't designed to deal with continuous loads (would need a heavier duty relay, and a dedicated wire from the battery to power the headlights), but works fine for momentary signaling.