The reason why the Vanette overheats is the radiator is mounted under the vehicle and the fan does not move enough air through it.

It was never meant to be sold in tropical countries.

Nissan in-house solution was to replace the fan blade with one with more blades. Works well enough as long as the fan motor does not start to fail.

With this in mind, any engine you choose, you have to give more attention to it's cooling system. Have adequate ventilation through the radiator.