None of the lights in your pictures are factory lights. Here are the correct lights for your truck. Only one on the rear driver side, most people add two and make them work as stop/turn, turn signals were not required in 50' two tail lights were only mandatory in Washington State.
https://www.flickr.com/photos/advance-design_parts_co/8326840990/in/set-72157632386552074
Multiple aftermarket options/lights were available as well as factory accessories.
https://www.flickr.com/photos/advance-design_parts_co/15240467973/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/16198650354/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/15330537489/in/set-72157631868452754
The front of a 50' again no markers or turn signals were factory installed, extra lights, turn signals, reflectors were all accessories also available after market.
https://www.flickr.com/photos/advance-design_parts_co/8250840647/in/set-72157632186114015
https://www.flickr.com/photos/advance-design_parts_co/15859482932/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/8129511072/in/set-72157631868452754
https://www.flickr.com/photos/advance-design_parts_co/8129416019/in/set-72157631868452754
(similar units for trucks).

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr