Cab top lights don't work

Ok, so I have a 1970 f350 with cab over lights. I just put new lights on and I know that they are grounded (they work when I plug them into another socket).

The wiring was a little messed with over the years, but is still decent. However, I cannot find the proper socket for the cab lights to plug into! Could someone tell me what to look for?

I am debateing just splicing into the other runner light wires, but wanted to see if I was just missing something obvious first.