[aerohead]

*If you're doing mostly highway,and maintaining a relatively constant velocity,the weight increase of the tires won't show up.
*Around town,you'll have more massive flywheels at all four corners,so technically,there would be a small penalty.
*The wider tires will have a slight aerodynamic penalty at speed due to their larger frontal area.
*And the larger aspect ratio,combined with the larger tire size is going to affect your gearing a bit,with fewer revolutions per mile,a little more difficult acceleration,more difficult passing,and hill climbing.
*The larger tires will also raise the Ranger a smidgeon which technically eats into its fineness ratio,roll moment,center of gravity.
*The 'rubber' gearing will slow the engines rpms and you may see a highway mpg increase from that.Especially with the streamlining.