Lexus GS300 1998 Owner's Manual page 173

COMFORT ADJUSTMENT
When not using the child restraint system, keep it secured
with the seat belt or place it in the trunk or somewhere other
than in the passenger compartment. This will prevent it from
injuring passengers in the event of a sudden stop or accident.
Your vehicle has anchors for securing the top strap of a child
restraint system. The anchor nuts are welded beneath the
sheet metal to permit installation of an anchor bracket for a
child restraint system.
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To install an anchor bracket, use an 8 mm X 30 mm X 1.25 mm
coarse thread metric bolt and a 15 mm (0.6 in.) spacer for the
outer anchors or a 10 mm (0.4 in.) spacer for the center anchor.
Note that the bolts accompanying many child restraint
systems are not metric. You can damage the anchor nuts on
your vehicle if you force bolts with different thread into the
anchor nuts.
For instructions about how to install the anchor bracket, see
"Top strap anchors and locations".
If your child restraint system does not provide any of the
necessary parts, you can purchase the following items from
your Lexus dealer.
D CRS installation kit
(Part No. 04731–22012)
– contains 1 bolt, 3 types of spacer and 1 locking clip.
D Bolt
(Part No. 91511–60830)