PWR Radiator vs External Tranny Cooler

[taylorbr]

With summer coming in the Mojave desert I need to prepare my car for the extra heat. Right now it is using the original radiator to cool the engine and tranny and I'm wondering whether I should move to using a PWR radiator or just adding an external cooler. I know there is quite a large cost differential between the two, but I'd rather go with the best solution, not necessarily the cheapest. I'm most concerned with: (1) will the solution cool enough that I won't have to worry about the tranny temp and (2) will the solution cool too much in winter that I won't have lockup. Thanks!