measure the dimensions of the opening. Make sure you have enough space for the lip on all four sides, approximately an inch or so. Let us know if it is tight.
No, we don't do custom sizes from cast iron. However, our sister companies make custom sizes in all sorts of materials such as steel, bronze, brass, aluminum, stainless steel, all sorts of varieties of wood. Go to the links page and link to one the sites from there.
Absolutely. These are the ultimate in heavy duty weight bearing registers.
Historic cast iron usually ships immediately. Unity collection is just a few days.