I've always run mine in series, i.e. Running the return line from the oe cooler into the supply side of the aftermarket cooler, then from the return of the aftermarket one goes back to the trans. Never hang the coolers by zip ties or any of them other cheap e-z setups that poke through the radiator fins. I always try and build a bracket if they don't come with one. Also, a no brainer, go for the biggest cooler you can fit in front of the condenser. I'm sure if you do some searching for "cooler" or something similar you may be able to find a write-up on how someone did their setup. You could also check f150forum as well.