Bart,

It sounds like you installed a 180&deg thermostat which would be fine for that engine. When you turn the motor off and the coolant stops circulating, it's normal for a mechanical gauge to climb. Hopefully the shop did more than paint the radiator black. At the very least it should have been boiled or reverse pressure flushed. If you can maintain a engine temperature close to the rating of the thermostat, all is well. If you are going to get real serious about the figures, you will need a accurate thermometer you can stick in the radiator filler and get a true picture of the coolant temperature.

Stuart