Hello I would like to help you
I assume that you have a transmission cooler on the from of the car as well as the one inside the radiator..
you want the fluid to enter the radiator and then flow out of the radiator and then trough the external cooler and back to the transmission. I would want it to flow in the top first.
so the answer to your question would be the top goes to the transmission output line.
I hope this helps you,
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