340 Water Pump questions, anyone using Flow Kooler?

You definetely need a shroud !!!!
Air takes the path of the least resistance.
Without a shroud, usually the air at the ends of the fan blades will get pulled. And it does not go through the rad.
With a shroud covering the end of the blades, all air being pulled has to come through the shroud and that means it has to come through the rad.

That is why all the manufacturers put shrouds on all their cars.