Thanks Karl. Yeah I'm thinking of eventuality putting one behind the grill. I did a bunch of reading... the external cooler should be AFTER the fluid leaves the radiator tank (??) and not pre- cool.
That makes sense as it doesn't get much heat before the trans... It picks up heat from passing through the trans... So it makes sense to put the cooler after it picks up heat from the trans...
If it's 80° out, then there is not much to cool...
But if the trans temp is running around 180°, then there is more heat available to cool...