Boy have you ever stepped in it; I guarantee that everyone who replies to this will have a different opinion, including those who say no thermostat at all.
Prior to the "Lean-burn" 80s and the advent of EFI, most factory applications used a 180 for best driveability and quick warm-up. IMO this is still true for street driven cars. The engine size has no bearing on thermostat application. Just determine the operating temp that you want to run at and size the cooling system to match. An engine with a 180 thermostat should run about 190 degrees. Horsepower = heat. The more power it makes the bigger the system it needs. /6s and Hemis both came with 180 stats, but the radiators were way different.
