Put this in the trunk CFG, under all the other slots:
slot 0.000 -0.015 0.210 0.000 -0.040 0.000 16 ; Registration
attach 0x0004D326 1
attach 0x0004D331 1
You may have to the position, though, to get it to work.
Same with this in the front bumper:
slot 0.000 0.050 -0.210 3.142 0.175 0.000 5 ; Registration
attach 0x0004D326 1
attach 0x0004D331 1