Not correct. My 04' calls for 5w-20 and so does my dads 03'. Either way I run 5w-30 in my 04' now that my warrenty is up, usually PP. Ford changed nothing in the 6.8l that would require changing from 5w30 to 5w20.

Using 5w-30 is fine for the OPs 99'. I wouldn't contaminate the oil with the Lucas additive. If you got a lawnmower with worn rings use the Lucas in that.