Jerry - the radiator tanks (on either side of the core) on almost every racing radiator are rectangular, and are regularly pressurized to well over 30 psi. My experiences in NASCAR racing showed no pressure split failures on the Cup stuff I managed a few years back. Here in the Charlotte area, if you need a custom radiator, contact Steve at Arrow Thermal Products in Harrisburg; he used to run production for one of the big aftermarket suppliers. vic