I am doing an oil-to-gas conversion of a 1944 brick Cape Cod and I am surveying the existing system. It has a hot water boiler and most of the radiators are labelled "National Art Radiator." They are small tube type radiators, section width 1 3/4", various sizes (most of them pretty large). I am finding VERY little in the way of resources for these. A search on here turned up a statement to the effect that they had standardized by that time and all companies small tube radiators would pretty much have the same radiation figures, but the link to those figures is gone. Any help?