do you have to have a gasket for a thermostat if has an o-ring on it? on 1998 Chevrolet Venture

for a 1998 venture

Asked by for the 1998 Chevrolet Venture
Most commonly you would not have a gasket when the thermostat has an o-ring. However, as with any rule there are exceptions. Your best bet is to look and see if there is a gasket or not when you take the old thermostat out. You local parts supplier will also be of help.
thanks for you help. RO