https://www.mamotorworks.com/corvette/product/corvette-1965-1979-rear-differential-front-yoke-install-crush-sleeve-624637
1965-1979 Corvette C2-C3 Rear Differential Front Yoke Install Crush Sleeve 3954483 - 3954483
Correct-shape crush sleeve for rear differential front yoke installation; helps set proper pinion bearing preload during service. GM ref 3954483.