I haven't seen any with the Benz nose yet, there are a couple around that I have seen with the Navigator front end.
As far as the Caddy nose being a conversion...The Caddy and Chevy are the same body. A guy at work just bought a nose from a wrecked Escalade and put on his Suburban.
Sweet looking ride.
Colt351, just as Weimer says the escalade(caddy) front comes off of the same bodystyle so they are direct bolt on swaps, but they also do sell aftermarket kits. As for the ford there are navigater front clips available aftermarket, but as for Benz front clips I have not seen one. Check Truckin' magazine, if its aftermarket its in there.