I have an 05 with the 4.7. On 35’s and put in 4.88’s a few months ago. I’m getting 12.5-13mpg (according to my scangauge). My commute is 26mi one way on the freeway I try to keep it around 75mph/2500rpm.
Like DOA said biggest issue is timing belt. Super easy to change just a ton of shit needs...