Big Block Dart Cooling

Changed out the T stat and bumped the timing back about 4 degrees. It was at 14. Took the car out this morning for a drive around town. Car got up to 210 in traffic. Got it home and it puked some antifreeze. I need to get a puke tank. I'll take it out on the freeway later. Oh, it's about 95 outside
I looked in a factory service book, all engines in 1968, had 180 T stats. why put a higher one in where its hotter out?? that lets engine get hotter sooner. also, you have way too much timing!!! usually put hotter T sats in when its colder out.