Interesting, I could just go to the body shop and lazer cut a piece to fit the same deminsions lol. I looked up the pc1750 and it will fit exactly in my truck. Do you guys think that would be a good buy? Im good friends with a dealer here in Kennesaw and can get one bnib with a 4 yr warrenty for 130ish.also.. I saw you mention about a place to keep the other battery. here is a kit to have a dual battery tray.. it's a bit pricey becuase it comes with an isolator and what not.. maybe you could just get the tray from them...
http://www.wranglernw.com/pc-6363-843-dual-battery-tray-kit-for-f-150ford-expedition-lincoln-navigator-1997-2006.aspx