Axles do not need to be removed to replace shocks. If may be a bit difficult to replace the shocks as the mounting may need to be bent a little to make the replacement possible.
As to brand, if you have a shock that is more or less horizontal then there is only one source. And Airstream dealer or Airstream. There is so little volume in these shocks no one else carries them because of the mounting. And in case you have the question as to why they did that .... to create more internal room inside the trailer.
Horizontally mounted shocks require different kind valving internally because the fluid inside follows gravity and is in a different place than a vertical mounted shock.
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!