Do I really need the wire from the alternator to the bulkhead connector?

In the arrangement shown below the number of junctions and fuses power from the alternator has to flow through has been minimized.
On the other hand, if you were using the battery to soak up some of the electrical noise, then the alternator output should be attached to the battery positive. In which case you ahve to put a link or maxifuse on the line.

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Obviuously the relays will need trigger wires. For examplem EFI and fuel pump needs to be triggered by the ignition start and the ignition run circuits, etc.

Note: Wire H1 is the power for the horn. It goes to the horn relay. No fuse on that until '73.