Former F150 owner here and this is from an F150 forum. I figured I need to cite it due to any copyright issues lol. It think it’s breaks down all your options pretty accurately.
This was written by member
ProZach.
I decided to start making a few FAQ threads. So here we go with a brief introduction and explanation of leveling (kits).
Intro: Leveling kits are specifically designed to improve the stance of your vehicle so that it appears (in a way) level. The four kinds are adjustable shocks, spacers, coils, and torsion keys.
Adjustable Shocks: These leveling kits are manufactured by bilstein and rancho. Bilstein is the most popular (and expensive) kit and rancho follows closely behind it. For the f150 many have complained of a swaying or loose ride with the ranchos while others have had no problems. Bilstein is said to offer a stiffer or firmer ride that most users are satisfied with. These kits work by adjusting the coil spring seat to a higher position on the shock which causes it to push harder back on the truck suspension as a spacer would and thus levels the front of the truck. One downside to both of these manufacturers is that rancho only offers 2” of level and bilstein only offers 2.25” of level. However you can adjust the shocks to different intervals from 0” to their max setting and no you can’t adjust the ride height once the kit is installed. The upside to these kits is that the suspension does not loose as much travel as a typical spacer so you won’t ride on bump stops as quickly or have other suspension problems as quickly as a spacer. You will need a spring compressor for either of these kits and it better be a strong one.
Spacers: The kits will vary from 1” 1.5” 2” and 3”, with many manufacturers across the board. The kits are made of different substances (iron or polyurethane) and have different things that each supposedly does, most is speculation with small amounts of evidence here and there. Basically daystar, who makes the polyurethane kit says that less metal on metal contact will help reduce wear and tear and offer a smoother ride, sadly these kits have been known to occasionally compress and not off as much as a level as an iron/steel kit. The iron/steel kit manufacturers boast that their kit will not compress and is usually made of some superior metal that again is supposed to help reduce wear. These kits (most of them) will cause rub of the upper control arm on the coil over spring, it’s nothing to worry about but you should keep an eye on it. You won’t need a spring compressor for this leveling kit, you just remove the entire strut assembly and attach it to the top of the assembly and reattach it to the vehicle. Also it is advised with most spacers that after every 3,000 miles or every time you off road to re-torque all the nuts involved with the kit.
Coil spacers: Coil spacers are another type of leveling kit that work similarly to strut extensions (or spacers). The main difference is the location of the apparatus. Strut spacers will attach to the top of the strut mount where coil spacer leveling kits will be placed directly on top of the coil spring buckets this will require you to use a spring compressor and the job will become much more difficult that going the way of a spacer. One other downside is that some people have complained of a stiffer ride.
Cranking Torsion Bars/Torsion Keys: These are one and the same. Torsion bars are another kind of suspension system. Basically they absorb impact. Many people will crank the nuts on these bars in order to increase the ride height of their vehicle. The same concept is applied with the keys only it’s a little safer than simply cranking the stock torsion keys. Aftermarket torsion keys have different dimensions and thickness in order to help the torsion bars compensate for the added torsion. Downsides to this way of leveling are that the bars can be over cranked and if this happens the ride can become very uncomfortable or even worse, the bars can break. To read all about torsion bars click on this link:
http://en.wikipedia.org/wiki/Torsion_bar_suspension
