That dog wont hunt
Ditch the electric fan all together and get rid of the mechanical flex fan.
Find 18 inch 7 blade ridge fan and a good fan shroud.
Swap out what ever thermostat for a high flow type stat, I use 160* in my 340
Make sure that your water pump is not being under driven, the crank pulley and the water pump pulley need to be at least the same size diameter. It would be best to even over drive the water pump for more flow thru the system.
This should help a bunch your next step is a 2 row aluminum radiator.
PS welcome to the forum, there's always room for one more.
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