someone long ago converted the distributor cap to a modern one with modern wires. To change back is it as simple as just replacing with the old style cap and copper connectors? The upper plate looks original.
There are a couple things to check, Make sure that the slot for the arm that adjusts the timing does not interfere with full movement of the lever. If it does there are a couple thing to do without widening the slot. Second, the copper strap for #3 plug may jump a spark to the rod that controls the timing. Just adjust the strap so that it is not near the rod and/or put a piece of rubber tubing on the rod.