The Motorcraft FL-820S has been reduced in size. It is now the same size as the Purolator PureONE. They likely use the same ADBV, so the PureONE should work as well as the Motorcraft filter does in preventing startup rattle.
The PureONE has its bypass valve on the dome end, rather than the base end. I have no idea if the new, shorter 820S retains the same bypass valve that it had before, or if they moved to the Purolator style, or even if the can is still thicker in the 820S than it is in the Purolator branded filters.
The PureONE has significantly more media in it than the Motorcraft, and the Wix has slightly more than the Purolator. I think if I didn't have a stockpile of the old FL-820S's, I'd switch to the PureONE, personally.
http://home.mindspring.com/~ed_white/id7.html
I'd like to see him dissect one of the new, shorter FL-820S filters.