Thermostat choice for my Duster 340

I'm a 150 miles North of you and only use a gutted thermostat, basically a restriction disc. Car runs at 170-180 on the highway or traffic. I have an old OEM with a 3 core in good shape, 6 blade flex fan and shroud.
The one or two cool fronts a year and it takes a few minutes longer to get to running temp. Both my cars also have no chokes.