We have a customer who has an old style heatilator. Firebox is completely cast iron (or was) that is rusted out, with masonry all around it. Clay flue tile. I am assuming a ZC judging by the vents along the top and bottom of the hearth. Replacement options? Client says he would like to have same cast iron firebox but are these even sold anymore? I would think they are completely discontinued. Any ideas on what we can offer the guy? Insert possible? Complete rebuild, if so what would be the best option for the replacement model??