Seat belts not locking up

[PurdueSD]

The seat belts in my 86 shorty will not lock up. I was reading that the inertia lock isn't working and probably needs rebuilt. BUT...

But, i also have young boys and would prefer the ability to manually lock the belt after pulling it to full extension. Was that not a built in function of these in 86?

If i can't fix these to lock or they are not capable of manually locking. Does anyone have any suggestions on a set to purchase? I'd like to retain the blue and stock style buckles if possible.

TIA