1965 Galaxie didn't have rollers on ends of spring. 1966-68 did. They added the rollers in 66 because of excessive spring wear and binding. They also changed the geometry of the z bar to get a better mechanical advantage and smoother action. I may have a 65 spring (new repro) let me look.
Now that you've explained it, I recall using one of the springs with rollers on another '65 Galaxie, but I had to open up the notches on the frame pivot and z-bar to accomodate the larger diameter. I'd rather use the '65 spring if you have one. Please let me know.