Something that I read a long time ago for SBC was to block the water passage that recirculates hot water in engine. It's the small hole on one side at the bottom of the water pump. I use a small piece of lead. And put the thermostat back in drill a 1/4 inch hole in it first. Doing these things makes sure that all of the water goes through the radiator.
Well thats my 2 cents anyway.
It works well in my car.