As Kev said there are many threads on this subject.
In which you will find much miss-information and in-correct advice.
To upgrade the plated weight of a vehicle can only be a "paper exercise" if the base vehicle was manufactured to a specification that allows the desired weight increase.
Often a change to some items on the van will be necessary, often simply tyres.
What cannot be done without mechanical changes is to raise the weight rating beyond the manufacturers design, no matter who you use.