I have seen them mounted underneath the car, but I wouldn't put it there... I plan on installing mine infront of the radiator. They are pretty small.

 

I have planned to but my intercooler right in front of the cooler underneath the frame so it gets pretty busy down there. But as it seems there is no specific place to but that tranny cooler right?

 

As far as i know there is no specific or designated place for one. Generally speaking though you would want it where it will get the most air flow i.e. the front of the car. But I understand you will have some fitment issues if you plan on running an intercooled S/C. Perhaps a phonecall to Summit or a stop by your local speed shop is in order.