The only reason a gas convertor will freeze is due to lack of water running through it.
Water in the convertor can be at 1 degree,because gas is below freezing gas it wont ice up.
As dattodude said run the water for the convertor through the heater hoses i dont think you will have a problem. & make sure the convertor is lower than the top tank of the radiator as an air lock will cause freezing as well. Also volume of water matters to so it must have good flow so take it from the water pump & some convertors have 1 direction circulation aswell so if you stuff that up it will freeze if it has that there will be a arrow or will say in & out on the or near the water outlets. So after all that i dont think a turbo will give enough water volume to stop the convertor from freezing