Was my truck a few years ago. '76 D100, 318, with 727 trans.
View attachment 1716333561
That year like your's was the most simple electrical system. Everything about that truck was easy to work on prior to onboard computers running things.
Liked that one so much that I found an '89 D100, 318 that I have now.
View attachment 1716333568
This one took some doing to convert it back to a non computer system and 4 barrel carb. Got rid of the in the tank fuel pump too.
☆☆☆☆☆