Lee,
I had the Timbrens on my 04 F250 and they did a good job. They reduced the rear-end drop to 1 inch or less and eliminated the bounce when towing thus providing better stability. I now have an 08 and I plan on installing Timbrens again. The best part about the Timbrens is they have no effect when not hooked to the 5ver which does not stiffen your ride at all when not loaded.