I believe that stock for both the V-6 and the duke engines are the 195*F thermostat. Running without a thermostat may cause weird idleing problems as the ECM won't go into closed loop operation, or take quite a while to do so. The thermostat should have a number on it on the end stating what temp is.
Edit for a clarification.
[This message has been edited by jetman (edited 06-18-2008).]