I see a lot of cages built with excessive triangulation, particularly in the over-head area. Just exactly where you don't want a lot of weight they've added a bunch of unnecessary tubing.
Look at how the A pillar tubes are placed with regard to getting in and out of the truck. When you see those tubes with all of the paint rubbed off right at the floor that tells me that the tube is in the way and shoes and boots hit the tube often. I know of no production cage that does this, but one way to gain back all of the door opening is to notch the dash and dive the A pillar tube thru it. That puts the cage in the way of the OEM p-brake pedal, but that can be dealt with. The Bronc-up was built this way, can take pics if there's interest.
Agree with above, either all the seats and all seat-belts are anchored to the cage, or all of them are tied to the body. And if you're going to tie them to the body then in an accident the cage is going to be moving differently from the seats and belts, which can make it more of a hazard than a help.
If you tie the cage to the frame, then it and the body will likely be moving and flexing in different directions and making a lot of noise. If you feel like you need more than just bolted to the body you can use those doubler plates that are supposed to be on the other side of the body for a second use. Add tabs to them and use "Hega Joints" on both ends of short tubes to tie those plates to the frame. Like this: