I'm confused by the contradiction of your statements.
The car is running hot at 200 while driving on the highway. I put in a 195F thermostat.
195F will open around 195F to an engine, that's very close to 200F. Running at 210F isn't very hot if you have stock fan settings.
The oil is milky, it is leaking coolant internally. We don't know what the issue is.
If you are using coolant internally, you have a serious problem that needs to be addressed ASAP. That is ..if your milky oil wasn't caused by a little coolant in the oil from doing the heads. Keep in mind the steel oil pan on most of these motors will hold 3/8" of lfuid below the drain plug. How much coolant is it going through? Is the engine burning coolant, you can tell by the exhaust.
Tell us more about the top swap. Parts you used for gaskets, if you sprayed the HG's with copper spray, if you used ARP bolts or stockers, or reused.
