Hi blwn31,
That sounds like a pretty impressive motor you have there, sure would be more fun driving than trying to sort out cooling problems. I would listen to techinspector on this one. If you dont have a shroud on the fan I would get one, if you get a nice tight one on there the fan will be more efficient when you are at low speeds or stopped. One of the things that we found in Australia with the LS1 motors was that the Aluminium blocks moved the heat so quickly that engine bay temperatures got quite hot, and the headers needed ceramics to try and keep the temp down. The aluminium motors also seem to come up to temperature faster, this is my observation with 2 LS1's compared to a cast iron 308 (holden) motor.

The best advice I can give you is to check out where your problem is exactly, ie is it cooling down at cruising speed etc, then you will only have to fix the problem once.

Good Luck