Things can be complicated.
As now you have an already taxed cooling system setup that is also setup to flow hot automatic transmission fluid through the bottom of the radiator first then on to the external transmission cooler.
You might ask how was the High Performance 440 in post #12 able to run cool with the 18" solid mount fan and no shroud.
One part of the successful setup was that it was a factory manual 4 speed car, so no hot transmission fluid was being pumped into the radiator.
Just one more piece of the puzzle that an independent external transmission fluid cooler may be a good idea as Bewy states above. Bypassing the need to run hot transmission fluid through the radiator, and that much less heat that you will be having to pull out of your cooling system.
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