Your truck has the wiring for a trailer built in. When you buy your brake control, get the correct wiring harness, it plugs in under the dash.
At the back of the truck there is a plug tucked up in the frame, probably on the right side. You buy another wiring harness and plug it in there. The other end of this harness plugs into the trailer.
These harnesses are standardized but you may need to change some of the wires because the standard has changed between 1966
and 2000. This is not difficult to do if you have the wiring diagrams which come with the controller and harnesses.
Look in the kitchen drawers and cupboards of the trailer. You may be lucky and find the original manuals, they will have the trailer wiring diagram. If not, you can figure it out by connecting the wires one by one.