A single fan actually covers more radiator surface area than the dual fan setup. The only advantage to dual fans is the ability to run just one fan unless you need both of them like on really hot days in traffic or running air conditioning. Most of the newer engines have dual fans but are designed to run hotter than the older ones for more efficiency which also requires the use of synthetic oil so it does not break down at the higher temperatures. My '65 and '68 run at around 175-180 degrees while my '95 has a temperature range of 195-220. Also, the newer aluminum blocks and heads dissipate heat much better which does not make them as susceptible to blowing the head gasket at higher temperatures or warping the heads themselves.
Also, on your engine, the water pump takes it's suction on the block and the colder water from the radiator enters the intake manifold first. This puts a large thermal stress on the heads by hitting the heads, (which are the hottest component except for the exhaust manifolds) with the coldest water. The newer engines have reverse cooling water flow where the water pump takes it's suction on the intake manifold and heads and cold water enters the block, which distributes the heat much better in the engine. The coolant has a chance to warm up from cooling the block before hitting the heads. Unfortunately, that is not a design change we can make to the older engines.
I have 2 fans on my '65, but they are both full size single fans set up in a push-pull configuration. One fan controls the engine temperature while the other controls the air conditioning. Probably could have gotten by with just one fan, but the jury was out because of where I live (Florida) and the really hot days running air conditioning a lot.
If you live Washington State and it appears from your hood you have a small block engine, I don't believe you will need dual fans, especially with a new Dewitt aluminum radiator which is much more efficient than the stock Corvette radiator. If you purchased the Dewitt with the fan package together, it even comes with a special shroud which allows air passage on the highway but practically eliminates air from bypassing the fan at in-town driving speeds.
Here is the Pull Fan controlled by engine temperature. I bought the fan and radiator from Dewitt as an package.
Here is the Push fan controlled by A/C needs. I bought it from Vintage Air and it was installed during the A/C installation.