Some nice ones here:
https://www.google.com/search?client=opera&q=Ford+F-150+window+gun+rack&oe=utf-8&channel=suggest&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=xIr5UeCwItbk4APvkIDoDg&biw=1736&bih=971&sei=x4r5UYqUHbiu4AOlnYHQCg
Cool...now I gotta go measure my back window... http://www.wingsupply.com/shooting-accessories/gun-cases-racks-ammo-paks-camo-kits/g-lox-quick-mount-two-gun-rack/