For me I would not have power steering for a number of reasons.
a) it will cost a fortune!
b) it adds additional weight - fuel cost will get worse
c) who can you really trust to do a great job at reasonable price
d) its a light van with no weight on the front, hence keeping your tyres pumped up (maybe a fig more than normal) helps and suspension greased at the correct interval (not lowered with fat tyres also helps!)
e) because it is a light van it is subject to cross winds, so the slightly firmer steering tends to help that, a super light power steering will make it far too easy to change direction and make it even more flowery in its lane control? Why do you think sports car manufacturers have speed sensitive steering? light at town speeds, heavier at fast speeds?
f) if you really must have lighter steering why not change to a steering rack conversion?
g) its a 1940's warmed over design not a T5 or Transit, what attracted you to it? Its simple , basic character features which this is one?
Sorry to be blunt but just my opinion....