I am leaning towards either the Timbren (TFR250SDE) or Firestone Air Bags (F2550).
I like Timbren for ease of maintenance and no air to leak. My concern is...since a 1" gap must be attained between the bottom of the Timbren and the top of the axle when installed/unladen, there will be some sagging when the camper is loaded. Obviously, not as much sag as without Timbren.
Air bags. Seem to offer the best solution when the camper is loaded. However, since 5psi must be maintained in the bags when the truck is unladen, the air bags will increase the rear ride height by approximately 1" according to some reviewers on eTrailer.com. This would be a big disadvantage IMO.
You just set the Timbrens to have clearance unloaded. Then adjust them as needed. They should contact the axle when loaded, if not, adjust them until they do. It's easy.
I have the Airlift bags. They have a bumper on the inside that smooths out the big hits before the suspension bottoms. It also takes up volume inside of the bag, so the bag is more progressive and build pressure quicker as it's compressed. So they need no air pressure at all. You can safely run 0. Keeping pressure in the bags is only to keep the bag from folding in on its self as your suspension moves, if it does that, it'll rub a hole. Usually, as long as your valves are in, you can get away with zero. Depends on your setup.
My setup is adjustable. I have it set so that 70 psi will not lift the trucks rear at all when unloaded. But as the truck is compressed the springs help more. You can decrease the distance between the top and bottom airbag mounts so it kicks in quicker. Even with 70 psi, my truck will be stiff, but level or even a inch low in the rear with the bags. I should adjust my bag mounts closer together, but I'm adding the Daystar spring cup which is thick enough to do the same thing. And that cup frees up the bottom of the bag so I have max off road suspension travel still.
The fifth wheel friendly Firestone and Airlift kits will allow more flex. But less roll stiffness and you have to watch exhaust clearance.
The types that mount over the springs will offer way more roll resistance, better for slide in campers and really heavy loads. But you have to be careful with tire clearance. These are usually kits that require frame drilling, even though the kit box say it's not needed. Lies, all lies! Just get a good center punch and you're GTG.
Either kit will limit downtravel and flex. Good for onroad towing and hauling. Not so good off road. The Daystar spring cups will allow your suspension to flex completely.
Air leaks are the least of my worries. it's just one airline connection per bag. And one valve in my bumper per bag. Don't waste your money on fancy pump kits or auto level stuff. These things are "set and forget". I just use a gas stations compressor, my garage compressor, or a bicycle tire pump under my rear seat. No big deal. KISS.
If I want the bags to kick in sooner and lift more, I just add steel bar spacers under the bottom mounting bracket to lift it up. The Kit came with an optional about 1.5" spacer thing.
No drill kit my ********:
As you can see. The bags are stretched out pretty far which is why my ride height isn't affected. The closer you set the mounts the more lifting action you get. The further, the less.
Installation was easy, thanks to the nifty cut out paper marker, but time consuming. Measure 100 times, drill once. If your mechanicly inclined, I'd do it yourself. I'm not to keen on a hitching post lacky drilling into my frame.
Plenty of clearance for my 295/70 r17 Cooper STT's on stock F250 XL wheels. Hopefully the Daystar spring cups will also clear well.
Daystar spring cups on a Toyota:
