LATCH systems should never be retro fitted to an older car, unless the car's manufacturer has an approved LATCH kit for sale. As noted above seat belts, when properly used on the car seat, do a better job of securing the seat then the latch system. It's just missing the convenience factor.
The following link is definitely a procedure that should not be followed.
http://www.instructables.com/id/DIY-LATCH-system-retrofit/
Excerpt from the site... Again this should not be followed. In the case of this fellow, If the car has no seat belts, have seat belts installed professionally.
And this is definitely a no no!
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