Believe by 69 they were fine spline. This was when Toyota was making changes all the time. I know the there are a few fine spline ball and claw axles out there but never heard of a coarse spline Birfield axle. To my knowledge only Lock-Right was made for coarse spline in this style locker...
Be sure you have the thrust washers for both the spider and side gears. Installed the Lock-right lockers in my 68 back in the nineties and know the spider gear thrust washers were removed. Can't remember the If side gear thrust washers were as well.