Big:
The headers are shortys bent out of pipe, not cast. The pipes run under the body far enough inboard that they can't be seen very easily. They turn out just in front of the rear wheels. I never really considered rear exhaust because of the difficulty of looping the pipes up and over the suspension. Someone will correct me if I'm wrong, but my recollection is that the vintage street cars (which is to say almost all of the 427s) required some extra surgery on the inner panels at the top of the rear wheel wells in order to make room for the pipes. Plus, I'm sure that I would have ended up with smaller diameter pipes.
My batteries are behind the passenger seat.
I honestly don't know the capacity of the tank. I'm pretty sure that it is larger than an original design street tank - it has extensions on the sides that stick out laterally into the space that would otherwise be occupied by the pipes had they gone over the suspension and back down at the rear. It couldn't all that much larger in capacity because I do have the fiberglass recessed trunk tray. Someday when I run out of gas I'll write in and tell you how much the tank holds!
Thanks for the nice comments on the car. The Ks do a great job and take good care of their customers. I like the simplicity of the appearance, though I also admire the more aggressive look of the 427SC. I've been thinking lately about painting it. Black would look wicked and it would be almost like getting a new car for a fraction of the price.