Duster 383 cooling issue

My dad tried 2 electric fans with his 440 and it overheated. He removed them and when for a drive with no fans and the engine ran cooler. On went a flex fan and issues gone. This was with an aluminum 3 core Champion radiator. The fans were on one of those shrouds that mount the two fans and actually limits air flow. I blame the shroud design more than the fans.

You mention auto tans. Do you have a large cooler in front of the radiator for that? The stack of radiator and cooler could be making one of the fans almost useless as it can pull through the two restrictions.

Like George said, if you have a mechanical fan toss it on and see.