Grill restoration...Few questions from the new guy

Hello all, didn't take long being here to catch the bug to rebuild an old gasser and I have a few questions. Firstly, I've read here about the lids porcelain coating and see that most shy away from one where the porcelain has worn through, is that more from an aesthetic standpoint or does it affect performance? Secondly, I see that there are differences between the LP and NG manifold orifices, are the burners themselves different between LP and NG? Lastly, I see that some will get a grill to use as a donor for parts needed by another. My question is whether the carts are interchangeable among different lines, for example could a 3 burner Spirit 900 cart be used for a Genesis 1000 or could a Silver B's cart be used for a Genesis 1000? Is there anywhere to find the dimensions(L x W) for the different fire boxes listed? Thanks in advance and any help is greatly appreciated.

Lots of questions. Though I think most would be answered with a search here I'll try and answer a few. The lid: it's primarily aesthetics. The coating does nothing for performance (unless you count rusting through part of performance LOL). Orifices: Depending on the valves used from the factory the difference between a NG and LP grill can be much more than "just orifices". As for the burners they're all the same. Once the proper level of gas gets past the valves the burners don't care what is put through them. As for the carts I don't know the answers to that

Dimensionally, the Genesis 1000 firebox slightly larger than the Silver firebox, so the carts will definitely not interchange.

The Spirit 900's firebox is more or less a match to the Silver, so the carts may interchange (they share the same burners and I've swapped a Gold manifold into a Spirit 900 before).

Regarding the porcelain I agree it's primarily aesthetics. My own genesis silver A that I restored a couple of years ago when I got it curbside had a small area of corrosion on the top of the porcelain hood. I sanded the rust off then touched it up with high temp paint. The corrosion hasn't gotten any worse and I don't think it will. But the spot is noticeable. But functionally the grill is fine.

Thanks guys!

This is a grill I picked up for $25 a couple weeks ago. It is going to be a rehab project. The lid is clearly dented and rusted where the porcelain has flaked off. If I just needed a grill for the sake of grilling, I wouldn't hesitate to use that hood. However it is a rehab project and since I already have a donor lid ready to go, I can just swap in a good lid. It wouldn't sell otherwise. But it certaily would work as is. It is basically like a 1950's junk car sitting in a field. The paint is gone and it is rusted all over, but it is thick steel and would take a decade or longer to fully rust through. In the mean time, there would be no compromise to the functionality of the grill.
But like I said, it won't sell that way, so I will strip the handle, two end caps, thermometer, hinge pins and WEBER Logo plate and toss the green porcelain hood and replace it with my black one.