Can anyone tell me which is the transmission pressure line and which is the transmission return line for the 2005 to 2008 trucks with an automatic transmission?

Also, If one were to add an aftermarket transmission cooler, do you tap off of the "pressure line" (to radiator) or "return line" (from radiator)?

 

Place the cooler in the return line. This lets the radiator start the cooling process. If placed inline going to the radiator any cooling could be reversed by a hot radiator.

 

Wondering why either line wouldn't work? My questions are they in series with each other or in parrallel (spelling)? Engineering stuff I guess.