A-Body 440 cooling problem

You might try checking the spacer between the pulley and fan. How far is the fan from the radiator? Try to get it within 1-1.5 inches from the radiator. This will insure a good draw of air across the cooling fins. A shroud would help a lot, but finding an original big block A-body shroud would be near impossible,( and wouldn`t work with your existing radiator anyway) however you may be able to find a 340/ AC equipped car to salvage one from.