:yeahthat: Most states motor registries have the same sort of advice.

For us we had to get DD a new seat at just under two. So she went from her forward facing baby seat to a MaxiRider AHR because her head was already above the top of the babyseat (she's very tall). The MaxiRider while very exxie comes with the harness and is also convertable to a H harness or just the lap-sash belt. Sadly at just 4 she's going to grow out of even the Maxi Rider soon.
Many do not come with the 5point harness.

Not sure what state you are in but in many the harness is mandatory. Up here in the NT for example it isn't. For us it's a safety thing, as was the ability to secure the seat via an anchor point (there weren't as many options when we bought ours).