A lower temp thermostat will not keep the temperture any lower, it merely opens the flow the radiator sooner. If the radiator and fan cannot keep the temperature at the thermostat opening temperature now, it won't with a 170, either.
The lower thermostat might have helped carbureted engines when the big ol' 4-barrel was sitting on an intake manifold that also carried coolant from one bank to the other. There was a need to vaporize the fuel for driveability. With port fuel injection, each cylinder gets the right amount of fuel and there is no coolant passage in the manifold anymore. A lower thermostat opening will keep the block cooler, keep the oil cooler, allow fuel to condense on the cylinder walls, allow fuel build up in the oil, allow water to not boil off... nothing good. You are better off with a normal coolant temperature and looking for ways to cool the intake air.
The other Gen 1 trick is a "Roe duct" in the chin. By creating an opening under the fascia (take a look at Dodge Intrepids) it allows air that would build up pressure under the nose (and maybe cause lift at high speed) to flow through the radiator instead. With a homemade version of this duct and the Gen 2 fan in my '94 I have never had temp issues since.