How does the Rallye Dash Tach hookup?

The 3 male terminals you identified aren't actually open. Those are buss bars. A wire connected to any one on a buss bar supplies power left and right to all the length of the bar. The additional tangs are only to allow chopping it to any length. So there is a 1 single a double and a triple installed there. So the one wire that feeds wiper fuse, radio fuse, branch cirscuits away from the other side of those fuses. Those smaller wires with tracers on the top in your pic ate branch circuits. The 5th male on the bottom is hot when you turn the switch to one but you can connect your wire there without an inline fuse before the tach connection. The factory didn't add inline fuses they only added a fuse and a terminal at the top right corner of your pic.
I don't think I can explain this any clearer. Maybe someone else can.