My approach to cooling has always been the same because it has always worked for me, engine swap after engine swap.
Same or larger square area that was used originally to cool the motor from the factory.
Same or more cores that were used originally to cool the motor from the factory (not to exceed three cores in my opinion).
Blocking of all air passageways where the air could get around instead of through the radiator core at the front of the vehicle.
Full shroud with the radiator positioned so that the fan blades are half-in and half-out of the shroud hole.
OEM 18 inch, 7-blade steel fan.
Thermostatically controlled fan clutch.
Water pump and crankshaft pulleys sized according to what was on the motor from the factory.
180 degree thermostat.
Sufficient openings in the engine compartment to allow the exit of all the air drawn into the compartment.
Proper coolant/water mix to prevent freezing up in winter. Water transfers heat better than coolant, but some coolant must be used to prevent freezing.
In 50 years of wrenching on cars, I have never used an aluminum radiator or an electric fan and have never had a cooling problem even stalled in traffic in Phoenix on the Fourth of July.
Part of your problem could be the fans on the front of the radiator blocking cooling air from going through the core. Just a thought.
By the way, are you the same guy with whom I discussed designing and building an independent front suspension several years ago?