383 pulleys....

Not familiar with big block clearance, but from his picture, the spacered fixed fan looked close with the cold case radiator.
With my small block '69 Dart, #2947 Hayden clutch, and Cold Case radiator, I had to chuck my aluminum water pump for the '69 cast iron pump, it's 3/4" shorter. I needed the radiator anyway, so got the proper Cold Case, inlet is on the opposite side of the aluminum pump. Do not know if you have that option with the big block.
Follow up, my Milodon water pump failed in under 500 miles, am in the process of installing a same Flowkooler pump right now.
Looks like the OP is going to try a shroud with what he has first.