If the new bars are drilled for wires, feed a pull wire in first, then tape it into the wiring bundle, loop a couple wires so it doesn't slip out, try to make them pointy. pull them in with a little lube, I use silicone spray. Pull and push at the same time, don't let the edge of the hole chafe the insulation. Sometimes you need to cut off the sheath because it's too hard and replace with heat shrink.