I found the following links for car seat reviews for size infant, combination, toddler & booster seats.
Check out the following locations for review of what may work best for you.
http://www.carseatdata.org/ has an impressive array of information for car seats including measurements of car seats, and links to several manufactures web sites.
This site would have been helpful when I purchased my convertible car seat as the one we currently own is a bit large; however, I think I still would have purchased it because of the good safety features for the price.
National Highway Traffic and Safety Administration Review for 2005 (last updated 1-10-2006
http://www.nhtsa.dot.gov/CPS/CSSRating/
Toddler & Booster seat reviews 5/06 on the Consumers Report Website.
Infant & convertible car seat reviews from 5/06 on the Consumers Report Website.
The following link describes the terminology used for car seats. It also has links to other review sites.
http://www.car-safety.org/guide.html
Have your car seat checked once it is installed. Find the nearest Inspection Station at http://www.nhtsa.gov/cps/cpsfitting/
