It's not a spacer technically. The front shocks have two slots for the spring seat. It would have a similar effect, but the arms are longer on the F150, so the effect is lessened a bit. Wheel bearings aren't going to be affected by the height or angle, as everything is aligned with-in spec, but the bigger tires would affect the wheel bearings.
A spacer would create more issues actually. Ask Zach, he tried spacers and the upper control arms got to bad angles, and contacted the coil spring all the time.
The only thing I might be semi concerned about is the upper balljoints. But they are relatively cheap and easy to replace. Some time down the road I want to run these upper control arms.