The frames are produced for Airstream, and have nothing to do with the automotive industry. The shocks can be purchased from Airstream, and I have read on these forums that they are produced by one other nmanufacturer, I do not know who. They must be able to work in a horizontal position, rather than a vertical. When you go to change them, instead of taking the axles loose, and dropping them, the brackets are made from mild steel, and you can bend them just enough to slip the old ones off, and the new ones on. Then strighten them up. That will save you hours of work.
Scour these forums for information using the search function. There is a wealth of info here.
2000 390 Landyacht XL
1989 29' Excella
WBCCI #6673 jerry Hodge
Have no intention of arriving at the grave safely, but rather to skid in sideways, chocolate in one hand,throttle in the other, totally worn out and screaming
"WOO HOO, WHAT A RIDE!"