What's the curb weight on the F150? Figure its actual weight is probably a bit higher than that, but close.
Late model F150's typically run between 5000 and 5800, depending on cab style, wheelbase, etc., so you are probably barely ok. I'd use it and keep an eye out for an upgarde to the 10,000 lb model. Watch the classified here on irv2, ebay, etc.
Former owner of 2004 American Tradition and several other RVs
Home is West Palm Beach, FL