Well first I would get rid of the 50/50 mixture. Use distilled water and only enought anti freeze to keep corrosion down ,say around 20%. Then add a can or 2 of water wetter.  Make sure all the air around the radiator is blocked off so all air has to go thru the radiator.  Decrease your timing a degee or so will help also.  A good spoiler will help too.  I've got a 454 and it runs 172-180 all day.  I have a flex fan on that one.