Reply from Sylvania light Company
Just thought I would share. This is the reply to the question....
What bulbs are available for the new 2005 Mustang GT
You should not try to upgrade any parts on your vehicle unless the original part number is contained in the upgraded part number. What I mean by that is you should not try to replace part 9145 with any part that does not contain 9145; you should not attempt to use part 9006 or 9005 in the place of part 9145. The only parts used in your vehicle that we offer any kind of an upgrade for would be your headlight and your fog light.
FOG LAMP 9145
Upgrade=9145ST (to be released in June 2005)
The SilverStar (ST) will offer a crisper whiter light than offered by stock and increase of approximately 20% more useable light than stock.
The XtraVision (XV) will offer the same color of light as stock but approximately 15% more useable light than stock. There is no SilverStar (ST) upgrade available for part H13. Unfortunately, we will not be adding this part to our SilverStar product line at this time. The National Highway Traffic Safety Administration wrote it into specification that this bulb cannot be coated. Although we can request a waiver, this is not currently in progress.
We would not recommend that you deviate from what the manufacturer has placed into any application. They have done the necessary testing to ensure that the lamps will function safely in their particular application. It is possible that you might damage the assembly due to heat emitted from a different bulb. Please do not hesitate to contact me if you have any other questions.