Intercooler with a Paxton unit is counter-productive. That unit will only put out around 6 maybe 7 psi max, so with an intercooler, even a very small one you will end up with 3-4. What needs a cooler is the unit itself. It is self contained using only Ford type F transmission fluid to cool it. There is a small cooler that requires an electric pump to run the fluid through the cooler. If you plan on driving a lot this is mandatory. Without the oil cooler, the unit will get extremely hot and I have seen some seize up due to overheating. This is one of the drawbacks of a self contained unit. You also have to change the fluid on a regular basis. The oil cooler is very effective though. The company below bought the Paxton SN2000 line. He repairs them and sells the oil cooler kit.
http://paradisewheels.biz/power/superchargers/