1968-1969 Mustang, Cougar, Montego, Torino disc brake spindles all the same. Can use 70-73 Mustang/Cougar or 70-71 Montego/Torino if you change the bearing out and use the outer tie rod to match.. In 1969 the Boss 302/Cougar Eliminator with Boss 302 got a spindle change which resulted in using a different wheel bearing and a tie rod with a bigger stud. These changes were done based on durability testing using the bigger wheels and tires used on the Boss 302. In 1970 this became the standard across the line.
The drum brake spindles are different then the disc so spindle needs to be for the disc setup. To use the later spindle you need to use the later bearings, spindle nut, and outer tie rod. Scott Drake is now reproducing this spindle if you want to buy new..