I have the F350 dually I tow 18k 5th wheel with pin weight of 4050 lbs. Truck squats 1 7/8
inches. Haven't added bags yet. I also get a noticeable launch vibration from 5-12 mph.

 

Just installed (had installed) the readylift 4" blocks. The truck looks like a truck and can squat a couple of inches without causing a reverse rake!


before


after

 

If you have enough of a load to get down on the overload springs, keep an eye on the rubber bump stops that hang down on the brackets at the rear of the springs. I tore up my first set at 10K miles, second set at 11K and third set at another 500 miles. Rather than stop at a dealer for replacements every 1000 miles, I bit the bullet and put Firestone Ride-Rites with an Air Station and automatic leveling valve on my F-450. My kingpin weight is 4,000 lbs. and the truck was squattin about 2 inches without the bags.

 

ive had good luck with supersprings had em on my 07 and now on my 11 quick and easy to install and maintain factory ride when unloaded and they are adjustable.