Absolutely just buy one that is convertible and says both rear facing and forward facing
It's recommended to rf till at least the age of two.
Quoting Rebecca R +1:" <blockquote><b>Quoting I'm His Amy He's My Rory:</b>" Radian?"</blockquote> ... [snip!] ... the straps out to make it a booster http://m.samsclub.com/ip/safety-1st-all-in-one-convertible-car-seat-marston/prod1420291"
I just got a MR65. Figured by the time he's 65lbs I'll just get a different seat. His happy a*s is rear facing until he hits 40/40.
I wanted to suggest to you to look at the Britax Convertible Car Seats. They have a bunch of different options for seats to meet varying budgets. The more expensive seats have added safety features that protect the child in a crash or added features for looks and comfort but they are all extremely safe seats. I bought a Britax Boulvard Convertible Seat for my daughter and we are very pleased with our purchase. It is a well designed car seat that is also great for looks and easy to install. The safety tests and standards are very high on Britax seats and I trust them to protect my child in a crash. I am a member of the Britax Saftey Squad but the opinions expressed here are my own.
I'd look into the Graco My Size 70. It's got the tallest rear facing shell. It's ALWAYS safest to rear facing and this got our guy to around 3.5yrs rear facing and now it's forward faced and lots more room to grow, still.