Alko suspension

If its the std (all in One axle,suspension) alko the only way I no is to block it at the mounting points, other than that you can order a new axle kit with the height required, I have have several made for boat trailers & if alko tell you six weeks it is at least ten
good luck

From memory the Aliner has a overlay beam axle.
Your alternatives are to have a straight axle fitted or a suspension riser welded to the chassis.
If going for the straight axle option oreder the replacement axle with a Camber Bend otherwise it'll be supplied dead straight which will result in increased tyre wear. This option wil raise the van around 45 - 48mm. For a short Aliner you'd certainly notice the difference.
A standard Chassis riser is 50mm.
Higher risers can be fitted as can a Spring over axle converion which will raise the van around 100mm, but that presents problems with the coupling then being illegally high.
Speak with your local van service man for the option that best suits you, but I've found over the years that a rise of 50mm (2") suites most vans very well especially the shorter ones like an Aliner.
Cheers, ozjohn.