I ran a 190* thermostat. So everything seems the same.
This is just a thought... Your battery is in the trunk. Where does the negative cable from the battery go to ground ?
I ask as (sometimes) the cable from battery is grounded to the rear frame rail.Many times this is fine and never is a problem. My Dart race car was a 13 to1 compression, it labored to start hot,fine cold.
A fellow racer said to run the cable from the trunk battery to the engine/bellhousing bolt. No labored starting after that.
Just kinda shooting in the dark hoping to find you a answer.