https://www.hemmings.com/stories/article/chrysler-8-3-4-inches-rearends
"Vehicles built from 1969-'74 used a spring-loaded cone arrangement called a Borg-Warner Spin-Resistant assembly to provide the locking ability of the differential. Both the Dana Power-Lok and the B-W Spin-Resistant limited-slip units are commonly referred to as Sure-Grip."