If it is not fuel injected and "you desire to use a thermostat" in the South my advice would be to use the lowest temp possible. There are some companies that produce a 160' for your engine. If it is a fuel injected engine there usually is only one temperature offered.
Edelbrock and FlowCooler are two that come to mind offering a 160'. Stant is a very good company also I think they offer a 165'
Many do not use a thermostat which is a debate much like what prop is best or what is better Coke or Pepsi.