I know that it isn't original and all, but when you trim the Mark VIII fan, it pulls soo much air on low. If you have a good tune on the motor, you will almost never turn it to high.
I was at a car show last year parked next to a judge with a clutch fan. His car was rock solid 190*. It was hot and humid and his car never budged. I asked him what he did to the motor and he said that it was all original.
Mine was at 170* with the fan cycling on and off on low. The sensor I have now turns it on at 195*. A little high, but is ok for cleaning out the carbon etc...
If I turn it on high it runs too cold in the winter. The 160* t-stat closes and the heat goes away.
HTH,
Dave