3/4 ton 270?
Truck was meant to be "used" when it was built.
Back in the "day", not much thought would have been given as to how much weight it could haul , but, how much would it haul.
They were not too fast on the highway, and the brakes were "State of the Art" at the time.
Change to a 12 Volt system which would accomidate the electric brakes on the trailer.