Pre 1968 linkage has bronze bushings throughout. I've seen some that were severely worn. In most cases linkage binding is in the wiper pivots. Similar short bronze bushings in both ends of those no matter which model/type linkage you have. You'll have to take them down, drill holes, and add zerks to grease them. Pivot seal kits include the zerks.
Pivots are held with 2 bolts so they can be flipped 180 degrees at reinstall. This puts the angular wear on less worn bushing walls. Just mark the bottom with a sharpie before you take them down. Rotate the marks to the top. They should run smoother and quieter.
