Tail, stop, turn lights:
For two element the brakes are wired power->4way flasher->brake switch-> turn signal switch->bulbs.
Turn flasher is wired power->flasher-> turn switch
So your fuse panel, wire harness and column all need to work together.
here is a 70s-80s typical GM wiring diagram. column connector is shown with the white wire at top. Wiring in the column takes care of how brakes, turn and 4 way get activated. I copied this to wire my truck from scratch and it works
I wired 3rd brake light from point shown by blue arrow as it needs to be independent of turn. Wired this way 3rd brake flashes with 4-way. You need two brake switches to keep it separate. My main brake switch is on pedal, but there is a currently unused brake switch on my wilwood adjustable proportioning valve, so I might redo that at some point.
In your shoes I'd probably bench test before assembling into truck. GM connectors and wire colors are a pretty common feature of hotrod wiring kits and aftermarket columns, so probably all compatible but easier to find out before you route wires.