That NGK number is one range colder I believe and they work great. Champion #71 also work great. platinum or irridium or other plugs are a waste of money and the platinum especially do not work well at higher boost levels, with an MSD, or with nitrous. Search previous rants by me about spark plugs for more info. Nothing works as good as copper, its the best conductor of the bunch. The only advantage to the platinum/irridum is htey are harder and thus last longer. They do not give better performance and usually are worse due to the poorer conductivity and pinpoint electrode designs (to overcome the poorer conductivity. Not to mention coppers are $1.50 each.
If you can't change your plugs AT LEAST once or twice a year, which is well wrth doing in order to check for lean/rich or detonation conditions anyway - sell your sports car and buy a nice Kia that only needs tuneups every 100,000 miles!