Heater core shot

I'm not sure the shroud was standard addition to a 68 340 A-body. In most OEM builds a sufficient radiator was all they needed. Thus the 3 and 4 core radiators. A shroud was added to factory a/c builds. A shroud on a 26 inch wide radiator is of more benefit than the shroud on a 22 inch wide radiator. There isn't a lot of the smaller radiator core that isn't right in front of the fan.