Measure the height of the radiator core to figure out what is the biggest fan you can install. An 11" or 12" aftermarket thermo fan will be sufficient to cool the engine down but the bigger the area you can force air through the better. The temp sender can go in the bottom radiator tank or in the thermostat base in the manifold somewhere. Sometimes there's provisions for a temp sender already in place (some thermostat housing top covers for Mitsubishis have one in them). There are also adapters that allow a sender to be installed mid hose. Look up water temp sensor joint pipe adapter on ebay - all the gear you need to set it up can be bought new for cheaps.