SPI LED Strips

I'm gonna be getting some http://www.adafruit.com/products/306 and I want to use them as under body lights for my car. I know its gonna be tacky, but I'm still a teen so I figured why not. I could not find a regulator that can go 12v to 5v with enough current. So I was wondering if the SPI protocol needs the same power lines like I2C or if I could add in power every meter or so? If any one has any ideas or questions let me know. Please and thank you.

You can add in power every meter but you have to connect the grounds

So I was wondering if the SPI protocol needs the same power lines like I2C or if I could add in power every meter or so?

Here is the link of one guy who explains really good

Tutorial 8 is about Spi and Tutorial 7 is about I2C http://www.jeremyblum.com/portfolio/arduino-tutorial-series/

I use L7805CV. Is the output current of 1,5A enough for you? http://www.produktinfo.conrad.com/datenblaetter/150000-174999/156048-da-01-en-SPANNUNGSREGLER_L7805CV_STM.pdf

If you need up to 10A here is the right one http://www.produktinfo.conrad.com/datenblaetter/150000-174999/156119-da-01-en-10A_POW_SWITCH_L4970A_STM.pdf

Note: All this product information I found on a german electronic shop called conrad.de . But I'm sure that this electronic parts you will be able to find in your contry.