Unless you are a purist, that idea they had is not a great way to do electrical. To have a more reliable connection with less exposure to the elements, do what was done later. Use a good sealed connector set or direct wire it. There really is no reason to have any connector. Sealed beam bulbs have a "connector" on the back for replacing the headlight. The least amount of connections in any electrical system, the better.
Packard 56 to be sort of era correct or all the way to weatherpack and beyond!
Otherwise
this or
this if you must.
I see you bought a factory wiring harness. Which one? Vendor? Part number?
