[RichardJ]

As 72SB is saying, if it ain't broke, don't fit it. Inline water pumps are not that particularly robust, so hanging the weight of a clutch and the stress of a multi blade fan does not sound like a good idea to me.
Inline Chevy six engines generally run fairly cool. I never heard of anyone describing the fixed 4-blade fan as noisy. 4-blade fans just don't move enough air at idle to make much noise. Once your truck is moving, you don't need a fan and the 4-blades don't offer much restriction to air flowing through the radiator especially without a shroud.

This sounds like one of those internet things like, if you don't convert to a internally regulated alternator, the sky will surely fall and your truck will never run again. Somethings done to these old trucks isn't always a necessary as others would have you believe. I installed headlight relays. I though the change in headlight voltage was marginal. I had just replaced the headlight switch and I hate farting with that damn button on the side of the switch and wanted to make sure I never have to do that again on this vehicle. Installing headlight relays is easier than that damn button on old switches.

If you are looking for more air flow because you are adding AC, then I think adding a electric pusher fan is a better idea. At least that was my thinking. I had to remove and modify the center support and hood latch in order to install the condenser, so I added the pusher fans at the same time. One fan runs with the CCOT system to help with the cycling and the other is on a 208* thermostat, but has never run.