Rally Dash Wiring Harness Questions

The non-rally dash harness I am adapting to rally is a 1972 Dart harness. It came with the round 12 position cluster as I think all 1972s did based on the 1972 wiring diagram from Mymopar. This cluster had the 9 wires in the non-rally positions, as opposed to the 8 wires in the rally dash. 2 of the 9 wires, Hi-Beam (Red) and Left Indicator Signal (Green) I removed from the cluster and put them in the 3-prong rally connector from the 1971 Rally harness. That left 7 wires in the 12 position non-rally cluster. I simply moved them to the correct rally dash positions based on their function. Even most of the colors were the same. My question is there is NO wire left to put in position #10. The 12v wire. The 1972 non-rally dash must get power somewhere? But it has NO 12v wire to move to the rally #10 position. I am thinking of 2 reasons for this.First---If you look at the 1972 non-rally wiring diagram for the Ammeter, the 12 gauge red (from Bulkhead Box J), and the 12 gauge black (from Bulkhead Box P) go directly to either side of the Ammeter. Wouldn't that power the whole rally cluster if they are all connected and are powered by position #10 in 1968? Maybe I don't need the 12v wire in position 10. The rally cluster would be powered without 12v wire in position #10. Second---They sent many more wires to the fuse box in 1972. The dark blue w/tracer coming out of Bulkhead position N is also 10 gauge in the 1972 harness and must have power b/c it originates from the line b/t the alternator and the ballast resister. I think that is how the non-rally 9 wire cluster is actually powered because the Ammeter in a 1972 non-rally is NOT connected to the 9 wire dash cluster. So I think the cluster will be powered by either/both of them. My question on that is can the rally cluster be powered by more than one wire source....Or is that a problem??? 2 12v power sources going into the cluster going to fry it? I only have a high school electronics education...but I can read a diagram. Tell me what you experienced guys think.