I don't have a part number, but the best fan I've used was a 18"-19", 7 blade fan from a '76 Chevy C-20 Camper Special with a 454.
I've also had good luck with a Derale 18" with a heavy duty clutch.
https://www.summitracing.com/parts/der-17118
What to look for in a fan.
Larger diameter - A larger diameter fan can move more air.
Increased pitch - Moves more air per revolution, but requires more power
More blades - may be quieter and offer smoother airflow.