Yes, the Monroe kit which I used was specifically for a leaf spring suspension. There was one specifically for a Torflex-style suspension (shown in the second article linked by GPJ) but it was discontinued, leaving only custom solutions.
Airstream adds shocks to their rubber torsion axles, which are currently Dexter Torflex; they have been doing this for decades.
In my case, the top mount hardware holds the shock a specific distance out from the frame, which must be enough to clear the air-assisted shock, which is typically quite large in diameter. The shocks I used are quite large, too, so an air shock might fit.
Originally Posted by Donna D.
I don't know air shocks wouldn't work, by why would you?
I don't presume to know the reason for the question, but a couple of possibilities are likely:
Air springing provides adjustability
. This allows the suspension to be matched to the load in the vehicle, just as with the rear of a tug that gets air springs pumped up when the trailer tongue load is added; this is rarely of much value in RV trailers (or motorhomes), which are nearly fully loaded all of the time. It also allows ride height to be varied, which can provide the ability to cruise on the highway in a low and stable mode, but creep through rough campsite roads and steep driveway entrances with more clearance. It could even be used to level the trailer side-to-side without levelling blocks (air-suspended motorhomes sometimes do that). At the time of my shock installation, I considered air shocks for these reasons, but have still not done it.
Another reason that many people consider air shocks is to boost a sagging suspension
. I would not do this, although another member posted about doing this with coil-over (not air, but the same general idea) shocks.