245/70r19.5 on stock f550 wheels

If my figures are correct....you do not drop much. A 4.88 to 4.73 or so. A gear swap in reality might be better option depending upon how much lower you want motor to run at say 60 mph. Along with how tall your highest gear in trans is. a drop to say 4.33's might be better in the long run. Along with the taller tires that I figured was a drop of about 3% vs the 4% in belows post.

Editing this to fix phat thums on smart phone and blankety blank blank auto correct!

Marty