Thanks for the response. I do half track half street driving on this car. For street you can't really avoid congestions in the heart of Bangkok. As for cooling, I still have the clutch fan, an oil cooler with a small fan, HPI 3 way radiator with the biggest cfm fan out there, as well as an extra small coolant cooler with fan. The airflow has also be designed to get ride of the heat while driving. The car is cool right now. I figure I can take on a bit more heat while removing the weight off the car as there is nothing else that I can do to improve the car within the limit that I want it to be. The weight should improve the handling of the car some what but I'm not willing to sacrifice the reliability issue for it.
You are right that people are not willing to put down that much money for just weight reduction, as a replacement to a stock streetable block. As the stock block continue to go up in value, if these shop advertize that billet block is replaceable to the stock block it should have better cooling than the stock block and have other better design features, which when I asked they refused to do it.