Originally Posted by Alberta Advantage
The leafsprings that come with the Carli kit (Deaver springs) seem to be very soft compared to the OEM springs. They'll sag a lot if you tow or haul heavy because Deaver doesn't use an overload spring. Carli's kit says it isn't compatible with air bags and even if it were, you'd ruin the ride of the Deavers by adding an airbag system. Not sure if you can use Timbrens either. However, if you're looking to go fast through the rough stuff and don't tow or haul anything too heavy or often, they'll be perfect. I guess none of this matters since you want a 6" kit. Just thought I'd add my two cents. When I do my lift, I think I'm going to get a Fabtech four link system.
I think "sag a lot" is an over statement. Yes they are softer, hence the great ride. Here are some pics of Sage towing with his full leafs. Doesnt sag THAT bad. http://www.powerstroke.org/forum/2876416-post6.html
As far as airbags, yes they will work with them, but I believe you have to contact Carli because some trucks need a bracket made for them to work. Airbags such as the Firestone air bags, can be disconnected in a matter of minutes if you plan to offroad.
They are not 6" lifts, but Chris (Super Diesel) bought his truck with a Carli kit, and it's atleast 6" up. Maybe spacers were used