Cant cool my 5.9 magnum. Radiator size or add one thing else?

I can tell you what works for me.
Summer temps here are about 90*F.We rarely have temps over 95*F.I am at 900ft elevation.I have an old 360 block from 1971,with aluminum heads,headers etc,dual 3" all-the-way exhaust,and a 230* @050cam.This, in a 3450 pound 68 Barracuda with a 4-speed,and 3.55s.Car goes 93 in the 1/8th.

I run a 26" factory A/C rad from a 73Dart, matching shroud,and 7psi cap.
I currently run 50% antifreeze, but it cooled slightly better with 100% water
A hi-flow Milodon W/P which is an 8-vane pump with an anti-cavitation plate.
A hi-flow thermostat that maintains a minimum 205*F
Anti-collapse spring in the lower hose.
Restricted bypass hose, and, in summer,blocked heater-hose circuit.
7-qt oilpan with 6 qts or so in it.
Fresh cold air to the carb
14* idle-timing,32* power timing, a 2-stage timing curve, that delivers 28* at 2800rpm, and 32 by 3400.I run a Vcan of 22*, that is all-in very early.
The carb is a little fat on the low-speed circuit.It runs 10.9Scr and 87E10.
A 7-blade A/C clutch-fan with a Thermostatic clutch from a Ford pick-up
I have a slight underdrive on the pulleys, cuz I rev this old girl to 7000 on a regular basis.

The factory temperature gauge never budges from it's "normal" position once the engine is warmed up, No matter the outside temp,nor how long it idles, nor how hard I abuse it.No track-work.Just a rock-solid 205*F.
The truck clutch on the 7-blader is a little noisy when it kicks in, but it reassures me that it is automatically taking care of my engine.And really it ain't near as noisy as the Ford fan was on the pick-up that I first heard this clutch working on;that monster fan roared! The 7 blade Mopar fan is quiet in comparison.
This system has been working since about 2000, no changes. Same hoses, second belt,some ignition timing changes; from time to time I still play with the rate of advance,just a bit.
I gotta tell you tho, same exact system, with a flex-fan and NO fresh-air, was prone to overheat at speeds under 25 mph. I had to maintain a minimum 30mph to keep the factory slow-as-molasses gauge happy, and a 15psi cap to keep the water inside the rad,lol.During this trying time, I removed the factory front license-plate holder, and cut the hole in the hood for fresh air,neither of which helped.The popular-brand flex-fan had to go.
What I learned from this was that at speeds over 30 mph, ram-air thru the rad was sufficient for cooling. But below 25mph, the fan had to be able to pull a lot of air. And the flex-fan no mater what rpm I ran it, just couldn't do it. Whereas even a small diameter 6-blade fixed-wing fan could. I mean that 6 blader was easily 3 or 4 inches smaller than the 7-blader that is on there now.
I won't tell you that you can't make your E-fan work, but are all three of those Magnums cooled that way? If yes, ................