here is the routing. The fluid will go through the heat exchanger before going through the KC. The heat exchanger will cool it before going to the KC and get even more cooler. i see the heat exchanger as a precooler. stock or aftermarket should be fine. i have the AFCO heat exchanger.
heres the thing though - when I had it on my lightning the intercooler res is AFTER the coolant comes out of the intercooler (ie at its hottest point) and the temps in intercooler tank were FAR below ambient. Running coolant through the heat exchanger (unless its pretty cold out) is still ADDING heat to the system that the KC must then remove