To find the exact cooling system capacity for *your* specific 1975 Dodge van, you should:
* Check your owner's manual: This is the best source of information.
* Look for a sticker: Some manufacturers placed a sticker under the hood indicating capacities.
* Consult a repair manual: A Haynes or Chilton manual for your specific year, make, and model will list the specifications.
* Check online forums: Dodge van enthusiast forums might have this information for specific engine options.
Without knowing the engine size, it's impossible to give you a precise number.