In V-8 hot-rod world, people find that electric fans do not move as much air as mechanical. People use them more for space considerations, simplicity, or bling. The Ford Taurus 2-spd fan is best. The little electric fan on the front of 300D's is mainly for cooling the AC condenser, and barely suffices for that.

A clutch-fan will be more economical. First, insure you have room. If too thick, consider a Jaguar fan since many hot-rodders use that when pressed for space, though I don't know if any thinner. I think all fit your water pump since Jag and 300D both bolt to my 1960's Mopar water pumps (I think GM's have a larger shaft OD). To avoid rounding the 4 bolts, you might get bolts w/ a larger head like I did (Ace Hardware, JIC head I recall). That lets you use an open-ended wrench on them. The factory bolts require filing down a box wrench to fit and you will likely round off the heads using the open-end side.

Re noise, you would probably do better by insulating the cabin. First seal all openings (vacuum tubes, oil pressure, speedometer, wires, ..., since sound direct thru the air is loudest. Then consider adding dampening sheets to the firewall and front floor (Fat Mat, etc). Muscle car owners do that routinely and it greatly quiets the car. You can go further and add to the inside of the door sheet-metal. Most effective is adding mass to the center of a panel to stop the primary vibration mode. Also, insure the weather-stripping on the doors and windshields seal tight.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans