Chevrolet 1993 Astro Passenger Owner's Manual page 46

Seats and Safety Bel&
Top Strap
AN155001
If your child restraint has a top strap, it should be anchored.
If you need to have an anchor installed, you can ask your General Motors
dealer to put it in for you. If you want to install an anchor yourself, your
dealer can tell you how to do it.
Securing a Child Restraint in a Rear Outside Position
K3138
You'll be using the lap-shoulder belt. See the earlier part about the top strap
if
the child restraint has one.
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