I don't understand how your turn signals are working ok. You have the right front, left front and rear stoplights all tied together so it seems like they all would be flashing when you flip the turn signal lever in either direction.
Well, the fancy smancy schematic capture software is on the work pc so here's something on a post-it.
The top shows what the 3PST switch looks like. The dotted line means all three switches are ganged together. It's not an electrical connection, just means they all flip or switch at the same time.
The bottom shows the two jumpers tieing all the inputs together. The input power comes from the emergency flasher. The outputs go to the right front, left front and the rear stoplights.
Pricewise, I think it's a wash so why not try posting in the "parts wanted" section and replace original with original?
You do not have the required permissions to view the files attached to this post.