where is neutral safety switch

Over the years, mfgrs would add harness connectors for nothing more than ease of assembly. A good example is the white engine harness connector added in early 70s.
Anyway... pre 70s owners will refer to the 3rd member of the bulkhead connector as the wiper harness connector only because it had no other wires in it. Since it had several unused ports, the mfgrs used 2 of those for the reverse lamp wires starting in 1970 when that switch moved from the shifter inside to the trans outside.
If you should need 2 of the male connectors to attach your reverse lamp wires there, NAPA stores have those. That Packard item number is here somewhere.
All you will need for the brown wire at your starter relay is a common female spade terminal.