My '72 250C has the Kangol lap/shoulder belts with the 'U' shaped magnetic coupling but my '72 250 sedan has Klippan 2-piece lap and shoulder belts where the retractable lap belt clips into the center buckle and the non-retracting shoulder strap has a pin that clips into the lap belt tang.
My 250 sedan must be a late '72 model as it has the seabelt warning light and buzzer, but thankfully, not the (universally hated) 'no-start' seatbelt interlock that was introduced in 1973! Probably one of the few instances of a Federal auto regulation being quickly repealed.
Happy Motoring, Mark