4way flashers on a 66 Barracuda?

Here's how these work "just for drill." The switch is special. It's 4 terminals, and off, each terminal is isolated. When on, all 4 are tied together. Here's how it's hooked up

From the hot buss/ fuse through a second (4x) flasher unit, feed power from the flasher to one switch terminal.

One of the other three goes to left front signal lamp, a second goes to right front lamp wiring, and the last terminal is hooked to the brake light switch wire going to the TS switch.

So when on, the flasher is hooked to those three places, and sends flasher power out to both brake lights and to both front lamps

Before these were OEM, a person could buy an add on kit and DIY