Pacesetter also makes "plain steel" long tubes for the 4.6L, but without CAT options. You would have to rig up your own set up for them. There is also a guy in NYC who was looking for a volunteer truck to work up a set-up for long tubes that his company would then market. Here is his contact email.
Nick@americanracingheaders.com
The only SC I've seen made specifically for the 4.6L F-150 was from Procharger. I've "heard" that some people have used Mustang SCs and modified them to fit, but I never saw a picture or actual item completed.