I'm the second "Unregistered"
. Yes, I would be leary of a Generations for a 36 lb child. You just don't know how long you'll get.
You cannot use both the harness and the seatbelt.
There are no Evenflos that harness past 40.
The Cosco Apex harnesses until 65, then becomes a booster. Its fairly new, but seems to be well-liked. Its a good price at $130 from Toys r Us, or some walmarts. It really the only combo to harness past 40 right now, so it has no competition.
A HUGE drawback is that you need a headrest in your car that supports the Apex's headrest. If you have short seatbacks it will not work. The mid-point of the child's head needs to be at or below the VEHICLE seatback/headrest. It will not work for us in DH's F-350.
Another option would be a Britax Regent. Its large, but comparable to the Apex in size actually. It harnesses to 80 and has super tall harness slots. People who have them LOVE them. Especially after being in an accident, you're probably game for all the security you can get!
There are three Britax convertibles that harness to 65, but for a 4 year old they'd probably only last another year or two. If you have a younger child to pass them down to, it might be nice. My DD is in one at 3.5, but I'd be leary to buy her another because she just moved to the top slots so I don't know that she'll be in it for another 2+ years, so there are longer lasting options.
HTH!
kelly