Pretty much whats been covered here. I think the timbrens cost a little much for what you get compared to an airbag system. And they cost nearly the same.

One negative about the airbags is that you're not supposed to lift the rear from the frame, causing all the axle weight to be put on the airbags. At least that what I remember the airbags I had on an old suburban said.
Another negative about the airbags if you don't have a compressor, many gas stations air compressors won't put out over 40 psi.

 

Finally installed Timbrens today and I thought maybe they sent the wrong set. When installed there was almost no space between the timbren spring and axle. I have owned this truck for 4 years and have never looked at the shocks, they look like they belong on a compact size car !! Also did not consider the weight of the camper shell. After checking around online I found the monroe sensa trac shocks with coil over. they claim to boost capacity 1200 pounds, Now truck drives and rides like never before.

 

i got those same style shocks but gabriel from autozone , they were only $49.99 for the pair !!
they are a little stiff with no trailer or load but work great with a load
here is a picture with 500lbs in the bed and trailer loaded