If you have only One light, you won't have signals! You would need to buy two more and mount one each side for signals only. OR....another taillight/stop for other side AND still need signal lights, Unless your turn switch has seven wires. On those the one wire from signal switch goes to the brake switch, under floor toe pan as said. It's real simple switch, with arm that gets held in "off" by the brake pedal arm, then springs to "on" when you push them away from the floor/switch area.
Whenever I get old truck, I buy one of those $25 or so trailer kits with two lights, side markers and wires. I also get some of that corrugated split harness tube to run it in. Use zip ties or metal or plastic clamps to bolt to side of frame, on inside. There are lots of holes to use. OR, can zip tie it to the brake or fuel lines running in same area also. I keep the trailer connector on and all. Run it up the engine bay area and go off of it with the smaller length mating connector to run to the fusebox and switchs. Works good everytime! Keep the Yellow and Green on correct sides like instructions, and you'll be all set. There is a place on-line for signal wiring diagrams, but I"m not sure address. Anyone? Should be some notes in the past, do a search here for them.
Rusty hood hinges??? Rust way up there??? Wow, how bad is the rest of this rig?? That's a new rust area to me. Usually the cowl is bad, but lower on sides.
