Just replaced the air suspension bags on my classic and decided to just replace the perished rubber rather than the whole unit. They come in about a third of the cost of the whole thing and work fine.
would recommend using if you're thinking about it...

http://www.island-4x4.co.uk/suspension-sus...27_28.html Regards
Mark

2009 D4; 1993 Classic 3.9 VSE