School me on seatbelts please

[brad2]

I have a 82 blazer. My back seat has three female ends and one male end. Two of the female ends are retractable. One the parts board I can buy three male ends and one female. Is it really as simple as combining these sets to have three sets in the rear? The two retractable female ends have me thinking maybe it isn't as simple as appears. Is there really supposed to be three seatbelts in the back of a blazer?
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