This is how i bought it

 

Typical electric fan set up,the idea is it doesn't take power away from the engine like a belt driven fan but they just don't seem to keep up especially if you don't have a 4 core radiator.
There's a couple other threads in here somewhere with others that has the same problem with 1st gen big block cars and electric fans.
It really doesn't sap that much power using a stock type fan with a clutch,it's not like a 396 is lacking to begin with . lol
I had a 427 in a '69 years ago,when I first put the big block in the car it still had a stock small block radiator and no shroud,ya she got hot even with a 7 blade fiberglass flex fan. Once I got the correct big block parts sourced used from an SS 396 roll over wreck parting out she ran much cooler.
As a bonus I also got the 3:90 12 bolt posi from that car,it was a good day!

 

Thanks for all the advice. I will look into putting a bigger fan with shroud but don’t know how much room I have with the serpentine system

 

I didn't notice that,it could present a problem no doubt so some research is definitely in order.

 

No, that is hot. When I said "it doesn't matter", I was referring to whether that was at cruise or at idle. Idle you will almost always run hotter since the only air flow going through the radiator is whatever the fan is producing. 210* is about normal operating temp for "most" vehicles. Yes, I know that sounds hot since water boils at 212* but chances are you're running a 50/50 mix, which, with a 15psi pressure cap, raises the boiling temp to around 265*.

With that electric fan set up, make sure they are pulling air in (towards the engine block). If they are pushing air, at high way speed, they would be fighting the incoming air when they run.

Adapting to a mechanical fan should not be too difficult. Fan clutch from a 3/4 or 1 ton truck/van with a big block (think 80s and 90s) should work. I can't remember exactly when the trucks dropped v-belts and went to serpentine but '87-88 sounds right but it could have been earlier. It's been a few years since I worked at a parts store so a lot of what I had to remember was replaced by other stuff. You can also look at Summit Racing for parts. If you do switch, you absolutely need to get a fan shroud, otherwise you're not going to get any benefit.

Also, check and see what temp. the t-stat is. Requires removal but a new gasket is less than $2, depending on the temp, you could go with one that will open a little earlier.

 

For the record, the type of fan you run has NOTHING to do with the problem you're having. When cruising at highway speed (where you say it's running hot) all the air movement through the radiator is from wind speed. The fan is totally useless at highway speed, this is the concept behind centrifugal clutch fans or flex fans.
First, check your ignition timing. Having it swung too far advanced or retarded will make the engine run hotter.
If you want to keep the electric fans, there's nothing wrong with that. But I would consider getting rid of that aluminum shroud, it's causing a dam effect, stifling air flow. Those holes above the one fan and below the other are there to help, but apparently it's not enough.
Again, at highway speed, your engine should be able to run with no fans at all without issue, fans aren't moving air at 60 mph. And yes, those temps are way too hot!

 

I first tried this setup. made it 7 miles. temperature went to 230*I was told the same thing about not needing a fan at highway speeds. so just for giggles I removed the fan setup ant went the same route after the engine was cool . driving55-60 mph, I didn,t make it as far as before.
I then got a 6 blade derale HD SS fan and stock shroud . 180* all day long

 

Welcome, John, to the neighborhood.
My suggestion is check the water pump, Since serpentine belt driven, is the belt driving the pump backwards (CCW rotation)?
If the belt is, is water pump a reverse-rotation pump for the serpentine drive?
With cap off, does coolant flow from core to tank - drvr side to pass side? If coolant does flow, this is good. If not, new pump needed.
If you add mechanical fan and clutch, you'll need ones for reverse rotation, look at '88-94(?) GM trucks with 7.0L engines.
Also, you may need to add air dams, 2X2 inch foam rubber across top of radiator support, GM did this with BBC with C60 (A/C), and a shield from the bottom of the valance to rad support. You could experiment with cardboard and duct tape and view results, as these two would prevent recirculation of air from engine around support back through radiator again. I believe GM also put sheet metal plates about headlight buckets plugging those holes.

About the temperature, when I bought my '88 Dually 7.0L new, it always ran 230-240 degrees. Back to dealer four separate times - too hot.
They said this is normal as long as it does not punk. Later in its life, I still have it, I changed to 160 thermostat and to no avail. I later changed from its OE copper/brass radiator to alum and gained 20 degrees with a 180 stat. I do see it open when driving from viewing temp gauge, then it slowly climbs to 210 degrees..