1. What year? I ordered a '66 fastback with dual exhaust.
2. Are the inside of the rear frame rails primered? Looking in the rails and the upper shock mount area, it looks as if all of the steel has had a silver coating applied to it. You can see some small scratches in the coating, like scratches in paint. There is brown primer in most of the rail, however.
3. Here are some torque box pics:

I tried to get better pics, but the frame is standing up against a wall and the bottom is against the wall. If you need better pics, I can get my son and we can hold it away from the wall for a better shot.
4. What is it coated with? It doesn't appear to be an epoxy primer. It seems similar to a body primer, enough to protect it through shipment and until you get it installed.
5. How much was shipping? From Canfield Ohio to MD, it was $265. Remember, if you want it delivered to your house, it will cost extra but it might be a better option for some.
6. Can you see daylight through any of the spot welds? I took a large flashlight to many of them, and nothing shone through. The worst gap is on the tunnel side of the driver's seat pan. Again, these look to be as good or better than the factory. Here's a pic:

I got the angle wrong, but in the middle portion of the pan, there is about a 1/16" gap between the seat pan and the tunnel. If I remember correctly, the factory gap was worse.
7. What gauge is the sheet metal? Using a sheet metal gauge, it showed to be 16 gauge.
Sorry about the large pics, I couldn't get them loaded into my album. I'll try tomorrow and see if I have better luck then.