GMC 1997 Safari Owner's Manual page 63

Securing a Child Restraint in a Rear
Outside Seat Position
You'll be using the lap-shoulder belt. See the earlier part
about the top strap if the child restraint has one.
1. Put the restraint on the seat. Follow the instructions
for the child restraint.
2. Secure the child in the child restraint as the
instructions say.
3. Pick up the latch plate, and run the lap and shoulder
portions of the vehicle's safety belt through or
around the restraint. The child restraint instructions
will show you how.
Tilt the latch plate to adjust the belt if needed. If the
shoulder belt goes in front of the child's face or neck,
put it behind the child restraint.