I would just buy a couple of them before going for all of them at once. The ones you get may not be to your liking... You have to learn how the LEDs are rated and get the right amount of LUMENS to duplicate at least a 40WATT incandescent automotive light bulb.
Some of the high end LEDs have built-in chips for a regulator circuit which will allow the LEDs to operate over a wide DC VOLTAGE range. These are know to radiate RFI Signals and may cause the HDTV to go to NO SIGNAL mode. This is especially true when using your OTA Antenna.
It may also interfere with any VHF/UHF radio operations like the WX RADIO, HAM RADIO etc.
I did all of mine in 2009 with a complete one time buy and this happened to me. Finally ended up with the cheap $4.99 LED BOARDS (cheaper in bigger qtys) you find on EBAY CHINA and they worked great here...

GOOGLE IMAGE
If you are camping much off your batteries this will be a hugh reduction in power requirements. Each 12VDC automotive Incandescant bulb runs very hot and pull around 1 AMP for each bulb on. That adds up in big hurry...
Roy Ken