Which Plug Part Number???

Okay, getting ready to attempt the spark plug change on my 2006 F150 5.4L FFV with 41K miles this weekend. I'm wanting to keep with the Motorcraft plugs, but getting different results. I've searched here, and everyone appears to be using various different brands and part numbers. So which am I to use? This is what I've found from a couple sites.

Motorcraft website for my VIN calls for SP507.
Summit website by year/make/model/motor (no option for FFV) calls for SP515
RockAuto website, only lists Autolite and Chamption plugs for FFV's, but has the SP515 for non-FFV 5.4L's.

Okay, I see that RockAuto has the SP507 listed as platinum, and the SP515 as double platinum. What's the difference? Should I just opt for the Champion plugs, even though I've never been a fan of Champion plugs?

 

Stick with the regular motorcraft plug. These motors do better with them

 

I picked my motorcraft plugs up at local parts house.

 

my computer at work also lists it as the sp515 motorcraft plug

 

Either SP-507 or SP-515 should do the trick... The 515 are said to be a double platinum but I can never tell a difference between the two or what that even means..