Does anyone know where I can get a replacement diff cover for my 04 FX4 4X4, Mine has not rusted but isn't very attractive either, Chrome, aluminum or simuliar.

Black SuperCab FX4

 

http://cgi.ebay.com/ebaymotors/Summi...QQcmdZViewItem
maybe this..

 

Seen these guys yet? Just a tad spendy judging by other sites that carry them.
http://www.oasisdifferentialcovers.com/ford.html

 

I've thought about this too, but wouldn't it void the powertrain warranty?

 

I have a hard time seeing how that would void the warranty. If Ford will maintain the warranty with a dealer installed lift, a new, stronger diff cover should be of no concern. I suppose you could have a dealer install the new cover just to be safe.