First thing as John mentioned is to identify your problem. You may have a broken temp gauge.
I personally prefer a mechanical temperature gauge (the one with the long spring steel cable and a bulb filled with mercury). With the power off it still reads the correct temp, so if you are overheating and stranded on the side of the road you can keep tabs on the coolant temp.
Second is my preference for a broad bladed fan (with the more blades the merrier), but coupled with a thermostatic viscous fan clutch that only locks up when the air coming off the radiator is hot. You are not saving any energy with a flex fan. It takes energy to straighten out those fan blades that the manufacture says saves you horsepower. As your grand father could have told you there is no free lunch. A fan clutch not only saves you energy but prevents the fan from spinning up in excess of it's intended operating RPM.
Fans will cavitate if spun too fast or shed a blade or three as happened with this flex fan in a Team Nova's SBC 406:
The other item in your cooling system is the water pump. Keep in mind that GM is interested in making money. To that end the car is designed very intentionally to be made as cheaply as possible. Your water pump has a Robert Fulton inspired paddle wheel moving water inside of it.
If you have ever ridden on a steam boat from the mid eighteen thirties you have no doubt gone astern to look at the paddle wheel beat the water to foam. Robert Fulton did a great job of installing a boiler and a steam engine on a boat that allowed it to go up stream or move against tide and light winds. John Ericsson (the marine architect who built the Monitor for civil war naval battle against wooden sailing ships also invented the "steam screw" or propeller used on all ships today (except at Disney World and excursion cruises on the Mississippi).
Aftermarket water pumps are not only made of aluminum to save six pounds off the front end, but had an enclosed impeller instead of a paddle wheel. Higher priced racing water pumps have a CNC machined scroll impeller as found inside a water well pump to move a lot more water with less effort.
Stewart sells a Phase Three and Four water pump that moves twice the volume of water with half of the effort (parasitic horsepower drain). Some people find aluminum offensive and abhor it's use on their ideal Camaro, but I would point out Chevy Orange engine paint sticks to aluminum just as well as cast iron. I have fooled a lot of people on the side of the road late on a Friday night with Big Chief heads painted Chevy orange.
Going back to your radiator it requires air to actually go through it not around it. If you have gaping holes in your core support or have the grill stuffed with transmission oil coolers and air conditioning condensers you may need an air dam as found on modern cars to prevent air from by-passing the radiator altogether. The air dam increases the air pressure built up in front of the radiator to push air through the core.
To test a gauge you put it in a pot of boiling water. It should read 212° degrees at sea level, less for higher altitudes. I compare mine to the readings of a Candy Thermometer that is accurate to a half of one degree in the same pot of boiling water.