Hi Marie.
The type of van is unimportant it is what tpye of tyre that is fitted that matters.there are two types of tyre that may be used, most vans less than 15 years old will normaly have radial tyres fitted.Others may have Crossply. It is important to make sure that all tyres are the same type. generaly ,pressures for caravan tyres are much higher than a simular tyre on a car, they need the higher pressure to suport the weight. the correct pressure is normaly found in the service book, if not, it may be marked on the tyre.it is very important that the correct pressure is maitained for safety and wear.
Hope this is helpfull if you need any further assitance come back.
regards
Jim M