Don't understand the wiki suggestion.
Right Patrick, what I'm saying there is (from Russel with Love, via Aidan) :-
Small length of chain (fairly beafy), or v.thick'n'strong strop
Trolley jack
Strong beam (scaff pole, short, say a 5' putlock)
A carabiner or shackle to suit hole in the mount (M10 clearance so 10mm will go through hopefully)
The idea is to jack up against the rear cross-member, against the ground, so effectively the van's going nowhere but upwards, exept that...
.. a chain is wrapped around a scaff pole or similarly strong beam, said chain (or strap) attached to the mount that needs pulling downwards...
the
TRICK being is that the scaff pole is
UNDER the trolley jack at the point of reaction where it will not want to slide a round fore'n'aft (this point is about int heory under the jack's pad when all the slack is taken up.
therefore to keep things symmetrical and satble, the chain or strap would need to loop around the pole either side of the trolley jack's chassis.
It was suggested I seem to remember, that if the facilites are available, a big tag, metal loop or similar (x2) be welded to the scaff pole to facilitate this exercise and stop the chain or tension member sliding orft, though I can picture it working just about, without.
Hope that helps, yours looks a fair bit worse than mine (just about 10° upward slant on only the nearside)
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Will look at the thread thingy too...
most of my damage is to the body work though. 
