[GuyBFF]

To avoid problems with corrosion I prefer staying all copper or all aluminum. Mixing metals works for some, but I still see problems with setups that have taken all the precautions.
For the same cost you could use BE coolings 12x5 tube fin tranny cooler, it's copper and cools within 1 degree of the stacked 12x5 coolers. In real-world testing it's only 2 degrees behind the best like Big Mamma or Black Ice (unless you use a peltier, this is where the efficiency of these big heater cores can make a big difference).