Running a 160 just delays the onset of heat. Might work as a restrictor once it opens and that might work out for you if it holds the water up enough in the radiator to lose the heat. I found replacing a 160 in a car I had made the oil stay much much cleaner. I put the factory 195 in it and it stayed right on the stat all the time. Even idling for long periods with no shroud.

The real deal is system capacity. Get that right and it will be fine. Engine masters did Dyno testing and a clutch fan without a shroud was the best engine driven setup. So I'd run a 180 or 195 with a big radiator and call it good. Get outside intake air piped in and you'll have a nice rig.