"I have a 1941 GMC 3/4 ton Pick up with a 248 cu inch engine. It now has an aluminum radiator, Air Conditioning; but retains the original 4 speed transmission."
Roger,
You may find that there was a factory fan shroud for your PU. In a 1936 Chevy service bulletin I found that there was one for my '36 Chevy PU and it took a diligent search but I did find one. Here's what it looks like. The '36 never had an overheating problem in the 55 years I've owned it but the fan shroud was irresistible because of the cool factor (pun intended) its rarity gives the PU.
If no factory fan shroud exists they're easy to make. This one on my 350 sbc powered '32 Ford roadster I made from a cookie sheet. In conjunction with a single 16" electric fan controlled by a thermal switch installed in the water pump casting it keeps coolant temperature between 180 and 190 in city and highway driving and even in gridlocked traffic on a 100* day the coolant temperature has not exceeded about 210*, and that situation is rare. My wife's 2017 Tahoe has a 210* thermostat indicating that 210* is not excessive. The Tahoe has basic electric fans like just about all vehicles now. So my experience is that a factory or generic aftermarket electric fan works fine, even on the small (16" x 26") '32 Ford radiator core.
