Got any pictures of how they mount it and if it is different than an OEM "spring" as GM calls them?
There are some options.

Rancho uses a drop bracket for the bump stops whereas tuff country just uses one giant long bump stop. Since it sits at an angle naturally, when it comes into contact with the control arm it has a tendency to just get pushed sideways til it just pops out. Stupid design really.

I thought I saw those in pictures of the total package on a few sites all layed out but,
I can't find a picture under an H3 of the set up how they were mounted.
I do know of some sources for something that might work if I could see how or what they are mounted to.

Ok got distracted, I guess they mount in the OEM cups?

In 06 or so when I made a set from two OEM springs or bumps I ended up with 1/2 longer to match the longer travel I found by extending a shock and longer anti-sway links. I just used those until a new type was made.
Timbren makes lots and lots of options I looked at.
I have not spent the time to look at all of it but at one time found what could have been used to replace the stock ones and some added length which could be made to work. Maybe some research would come up with the right combo.
The H3 and H3t are listed but I guess you would need something longer cross referenced. They have rear ones also.
http://www.timbren.com/timbren-appli...pdfs/GMFC4.pdf
This is a just a sample to show types of mounts. It just happens to be on page for a complete system of some kind.
http://www.buyautotruckaccessories.c...FUHatgod_QxeJw

ps, ok I found a picture of the Tuff Country mounted in the OEM cups but it is in Adobe format and I can't just pull the picture.
There should be something Timbren has the would work, probably better.
Hope that helps you start on the trail to a solution.
Would it be too simple to get some mounts from Rancho if they part it out?