I would always go for Heavy duty in a van, they probably want to know if Air conditioning is involved that requires a heavy duty radiator. or at least a little more. but with vans pushing more air and with a high top or more Flares and spoiler and the engine is contained in a little close fit box Heavy duty never hurts
Been There, done that, Member of those....
Built for comfort not for speed
....Well speed too !...
I am a vanner, Promise me the world, give me nothing, I'll be back ... next year !