You really want to do it, don't you??
I would be 100 times better to isolate your air filter from the engine, for example with a heat shield, and get cold air where it is, as close of the road as possible. You could draw a flexible hose from the passenger side air intake on the front bumper to the engine room. Lots of NA owners (not only supras) do that here as the ambient air is warm and has a lot of humidity in it, it works pretty well from what I've heard, it's cheap, and you can revert it back to stock in 5 minutes.
Concerning the cooling of your engine, the stock system is fine even if you push it uphill on a summer day for a long time. The temp gauge has never moved an eyebrow on mine on these conditions. That's for an 99% stock motor. One more point, it's not good to cool the engine down too much on a stock setup. Engines are designed to work at these temperatures, they won't get hurt anyway as soon as your engine oil is fine and matches the manufacturer standards.