engine still not cool enough

I have a 67 Dart with a 340. I have put in a new radiator ( 70-72 dart style ), the matching shroud, factory 18" 7 blade clutch fan with the short jaguar clutch. THat gave me 1 1/8" clearance between radiator and fan clutch. All of this has helped cool the engine some, but not enough because summer is not even here yet. Went for a short ride last night ( 55* ) and car ran at 185*. got home and let it idle about 15 minutes and it stayed about 195*. Before the clutch fan it would get over 200 idling. It has an 8 blade pump and 180* thermostat. Could the water be moving too fast too cool at idle? If it takes buying an aluminum radiator I will, but I would really like to make the stock cooling system work if possible. Any ideas?