I just got a confirmation email yesterday from Derale that they do not make any transmission coolers without aluminum turbulators inside them. Flex-A-Lite is another big manufacturer, but I haven't had a chance to ask about the turbulators in those coolers. If you don't want to mess with aluminum, you're pretty much going to be limited to heater cores or commercial water cooling radiators. I've been looking without luck for a while for a thin copper radiator large enough for 4 120mm fans. If you find exactly what you're looking for, be sure to post it
