regardless of which brand you use, there are two considerations you want to keep in mind. type and size. i used the old fin and tube type oil cooler for years, then recently switched to a stacked plate design. the stacked plate design cools better for the given amount of space. my old tube and fin cooler had a larger surface area than the stacked plate type, but the stacked plate type cools better. also the stacked plate design tends to be capable of withstanding higher internal pressures. also, they're not as easy to damage. also the size is a factor, not just in the cooling efficiency but in where and how you can mount it. you want to put it where it can get a good volume of air flowing across it, and also where it will be reasonably easy to replace the lines if need be. ebay has alot of cheap tranny coolers. if i had the room and a charging system that would support it, i would go with one that has a mounted fan on it, just for extra insurance. good luck with your project.
I have a B&M with a fan. I deleted my foglights and mounted it right behind the opening for the passenger side fog lamp. I have yet to have the fan come on, it cools well enough with just normal air circulation.
Just a side note, Art Carr will NOT warrenty their transmissions if a Tube and Fin cooler is used. They said it will clog up and burn the trans up eventually. Stacked plate seems like the way to go. Yes, it's about 3 times the price but you will only have to do it once.
I know people are getting away with tube and fin type coolers, this is just what I was told by Art Carr.
If you have a set-up like RC (with a fan), you can mount it about anywhere you like (I've seen them in the rear of cars before - kinda trick as long as it's all well shrouded).
Otherwise, you will probably want the cooling fan to be able to pull air through the new cooler. This does drive more hot air into the other coils, but if your radiator is in good shape and you have a decent fan, it should be fine.