Found this ,, thought it was intresting Actually the full endurance package was not introduced all at once. From 1987 to 1990, in models 29-3, 29-3E, 29-4, and 29-5, the Endurance Package was introduced as a series of improvements. Interior parts were fitted tightly, studs were radiused, a new yoke retention system was designed, a bolt block was installed, and the cylinder locking bolts were cut