Ranger is a tall drink of water. His atypical height and skinny build wreak havoc on finding pants and car seats that fit.
Since our beloved Graco infant car seat, we've gone through a number of convertible car seats that really didn't merit particular mention. Ranger quickly exceeded their 40" to 43" height restrictions (remember that kids with long torsos can outgrow a seat before they hit the height total requirement).
We bought a Britax Regent (max height: 53") for our primary car (a Honda accord) and my mom's minivan (the cars he rides in most often and on long trips). We chose it for it's five point harness. Upon first inspection, it looked like it wouldn't fit in my car. With a lot of wrestling, we were able to get it in place. It's huge in our small car, but seems both indestructible and luxurious (we call it the recliner). It's much easier to install in a LATCH vehicle (like my mom's minivan).
For Jim's car (compact sedan) which Ranger rides in less frequently, we have a Britax Parkway (height limit: 60"). It's a compact booster that uses the car seat's belt instead of an attached harness. We like it, but feel it's one he will do better in when he's more mature. We have to be attentive that he doesn't try to slip his shoulder out from under the seat belt mid-trip. He's starting to understand that we want him to leave it alone, but it's much easier to use (and feel confident in) a five point harness at this young age (2.5 years).
If you're currently looking for a Britax seat, all Britax is on sale 20% off at Amazon through Sunday, March 2nd.