I can't help with the 170 engine, but I had horrible issues with my 347 engine overheating and went through most of the same type fixes trying to cool my engine off. It would boil over no matter what I tried. I purchased an aluminum radiator originally, tried electric fans pushing because there was no room on the engine side. Still boiled.
I tried different thermostats, no thermostat, different size restrictor plates, got rid of the electric fan, tried different types of blades on cooling fans, on and on and on.

I finally ran into a guy at Hot August Nights. He saw my issues and told me his solution to the same thing. He had just installed a new four core radiator from Champion and went back to the engine fan.

I got home ordered the same radiator, had to modify my frame and cowl to get room for the radiator/fan. Now it runs at 185 degrees no matter what or where I go.

But, my brother Jerry with his Fairlane has done what I have and he must have the engine from Hell that Roger talks about.

May not be any help. ?? Larry